Most of what circulates about this breed is either a joke about zoomies or a vague warning about cancer. Both undersell it. The Boxer has one of the best-measured health records of any dog, and two chapters of it are hard. One is a disease of the heart muscle that a normal check-up will miss. The other is a tumour rate genuinely higher than in other dogs of the same build.
Neither is a reason to talk you out of the breed. Both are reasons to know what to ask for, and when.
What the panel can tell you, and what the standard leaves out
The American standard asks for a “medium-sized, square-built dog of good substance with short back, strong limbs, and short, tight-fitting coat.” It sets height at 23 to 25 inches for males and 21½ to 23½ for females.
It sets no weight whatsoever.
So the weights in the panel above do not come from the standard. They come from a measured population of pet dogs, which is why they can be split by sex with any confidence at all. Our methodology page sets out where each breed’s figures come from and how much to trust them.
One practical note on shape. Height finishes before weight does. A ten-month-old Boxer can look its adult height and nothing like its adult self, because the chest is still filling out. Our guide to when puppies stop growing covers why the two run on different clocks.
Temperament, and the one row of data that is actually about Boxers
Start with the ceiling on every breed description ever written. When researchers matched owner reports against DNA in 18,385 dogs, the breed a dog belonged to explained about 9% of how it behaved. Nine tenths sits somewhere else: in the individual dog, its people, its life so far.
With that said, this breed does have its own row in the classic aggression survey, and it is worth reading properly. That study scored 3,791 dogs across 33 breeds on a validated owner questionnaire, counting the dogs whose owners put them at the top of the scale (“snaps, bites, or attempts to bite”) on at least one question in each category. Seventy Boxers were included.
| What the owner reported | Boxers | Share |
|---|---|---|
| Toward unfamiliar people | 4 of 70 | 5.7% |
| Toward the owner | 0 of 70 | 0% |
| Toward unfamiliar dogs | 11 of 70 | 15.7% |
Two very different results in one table. Zero owner-directed aggression puts the Boxer among only six of the 33 breeds at nought. The dog-directed figure of 15.7% sits in the upper half, though well below the top: Akitas came in at 29.3% and Jack Russell Terriers at 21.8%. The paper’s list of gentlest breeds names Golden Retrievers, Labradors, Bernese Mountain Dogs, Brittanys, Greyhounds and Whippets. The Boxer is not on it, and we will not pretend otherwise. In UK vet records, aggression was written into the notes of 90 of 3,219 Boxers, 2.80%, in a single year.
The first two years
Adolescence arrives here on the same schedule as everywhere else, and knowing the shape of it stops you blaming yourself.
Guide-dog puppies were asked to sit at five months and again at eight. Ninety-three dogs took that test (Golden Retrievers and Labradors), and at eight months they obeyed less, but only for the person raising them. Handed to a stranger, the same dogs did better. A separate group of 285 dogs in that project was rated by questionnaire at five, eight and twelve months. Keep those two apart; the carer-versus-stranger result belongs to the 93.
A British cohort study then followed puppies through their whole first year and a half. Owner complaints peaked at twelve months, where 513 of 1,219 dogs (42.1%) had at least one problem behaviour reported.
The sit test used retrievers only, and the cohort study pooled every breed, so take the timing rather than the detail. What is specific to this breed is what else those two years are for. Boxers are a large breed with a fast, athletic build, so the growth-rate cautions apply: read our summary of growth speed and joint problems and of what large-breed puppy food actually changes. This is also when heart screening starts. The breed club asks any dog being bred to wear a Holter monitor from twelve months.
The heart: a rhythm problem, not a murmur
Arrhythmogenic right ventricular cardiomyopathy (ARVC, and usually just called Boxer cardiomyopathy) is a disease in which working heart muscle is slowly replaced by fat and scar tissue. The replaced muscle fires extra beats out of turn. A long enough run of them can drop the dog, or stop it.
Here is the sentence that matters most on this page. A Boxer can die of this with a normal heart scan. In a prospective study that followed 72 Boxers over eight years, 49 of them affected, 47 of the 49 kept normal heart-muscle function for the whole study. Fifteen died suddenly. Sixteen, 33%, fainted at some point. Median age at diagnosis was six years, with a range of one to eleven.
That is why the screening test is not a stethoscope and not only an ultrasound.
The DNA test, and what it does not settle
A deletion of eight DNA letters was found in a gene called striatin, on chromosome 17, by a genome-wide scan in 2010. Striatin sits at the intercalated disc, the join between one heart muscle cell and the next, alongside three proteins already known to fail in the human form of this disease. Dogs with two copies of the deletion had significantly more extra beats than dogs with one.
A follow-up compared 33 Boxers with dilated cardiomyopathy against 29 with ARVC and 16 healthy controls. Thirty of the 33 dilated cases carried the deletion. Three did not, which the authors read as proof that “there is at least 1 other cause of DCM in the Boxer dog.”
Then it gets harder, and a buyer should hear this part. A UK pedigree study of 183 ARVC-affected Boxers traced every case back to a small group of imported American dogs, then checked the genotypes. Its conclusion is blunt: “Dogs with and without the STRN mutation were found in both ARVC affected and normal Boxers showing that the mutation is not responsible for the disease.”
The lab that runs the test says much the same in gentler words. North Carolina State calls ARVC “a disease of incomplete penetrance”, and notes that “some individuals with the mutation may never show the disease.” Dogs with two copies “appear to have more significant disease.” Their advice is not to test and relax. It is that “Holtering be started at three years of age and repeated annually.”
How incomplete? The same team put it at “approximately 82% in positive heterozygotes … and nearly 100% in positive homozygotes.” Read the rest of their sentence, though. They measured penetrance “as evidenced by the development of ventricular arrhythmias”, so those figures count dogs with extra beats, not dogs that fell ill. Set that beside the pedigree study and you have two groups disagreeing about whether the variant causes the disease at all. That is the honest state of it.
One oddity we could not resolve either. OFA’s registry holds 393 Boxer ARVC DNA results and grades 2.5% abnormal, which ranks the breed first for that test, though we cannot say how many breeds are on that list. A welfare review reports a very different early series: of the first 1,690 dogs tested, 53% were negative, 41% carried one copy and 6% carried two. Those two datasets are not counting the same thing, and the OFA export does not say how it handles a single copy. Treat neither as the breed’s carrier rate.
The test that actually screens: a whole day of heartbeats
A Holter monitor is a small recorder worn in a jacket that logs every beat for 24 hours. What it counts are ventricular premature complexes: VPCs, extra beats fired from the lower chambers. The published bands look like this:
| VPCs in 24 hours | How it is read |
|---|---|
| 0–50 | normal |
| 51–100 | indeterminate; repeat in 6 to 12 months |
| 100–300 | suspicious; repeat, and do not breed on it |
| 300–1,000 | likely affected |
| over 1,000 | affected |
The eight-year study above drew its line in the same place, calling a dog affected at 300 or more VPCs in 24 hours on at least one recording, and calling a dog a control only if it reached six years old and never exceeded 50.
How many Boxers cross the line? Nobody has measured it across the whole breed. The best figure comes from Holter recordings on 301 clinically normal Boxers aged one to sixteen, in which about 23% had more than 90 extra beats in a day. The same review says plainly that it is “not aware of any data on the proportion of animals that develop the disease.”
Why one recording is not the answer
This is the part most owners are never told. Beat counts swing enormously on their own. Ten affected Boxers wore a recorder on seven consecutive days, and spontaneous variation alone explained as much as 80% of the change in beat count in dogs with frequent arrhythmias, and close to 100% in dogs with fewer. So a count that halves after starting a drug has told you almost nothing. The same eight-year study saw dogs drop back into the normal range and then climb out of it again.
Two documents make this concrete for a buyer. The American Boxer Club asks for a Holter from 12 months, repeated annually for any dog being bred. And OFA will not issue an adult-onset cardiac clearance here without one. Its rule names the breed: “Boxers and Doberman Pinschers also require a Holter test within 90 days of the cardiologist’s examination.”
The other heart problem, and it is congenital
Subaortic stenosis is a ring or ridge of tissue narrowing the exit from the left side of the heart, present from birth. A referral hospital reviewed 80,943 dogs seen over ten years and found 259 cases. Boxers accounted for 34, which was 2.27% of the Boxers seen there, at an odds ratio of 17.23 (95% CI 10.51–28.23). That was third highest of any breed with at least ten cases, behind the Bullmastiff and the Newfoundland. An odds ratio of 17 means the odds are seventeen times higher, not that seventeen times as many dogs have it.
The breed club asks for a Doppler echocardiogram at 24 months to check for it, once. OFA’s congenital cardiac database holds 4,404 Boxer exams and grades 0.7% abnormal, plus 1.5% equivocal: a low figure, from dogs already picked for breeding.
Cancer, and how big the gap really is
This is the other half of the record, and it is unusually well measured.
In one year of UK primary-care records covering 3,219 Boxers, neoplasia (tumours and growths) was recorded in 457 dogs, 14.20%. That was the second most common disorder group after skin problems. The authors set it beside other breeds of similar size drawn from the same database: German Shepherd Dog 4.82%, Greyhound 5.5%, Labrador Retriever 7.4%, Rottweiler 7.96%. Same records, same year, same method. The gap is real.
It shows up at the end of life too. Of 346 Boxer deaths in that study, the largest named cause was neoplasia at 43 dogs, 12.43%. A further 29, 8.38%, were recorded as a mass lesion. The single biggest entry was “death – unrecorded cause” at 73, 21.10%, which is a limit of the data rather than a finding.
Mast cell tumours. These are the best-measured of the breed’s tumours. A study of 168,636 dogs in England found 453 cases, an overall prevalence of 0.27% (95% CI 0.24–0.29). Boxers came top of every breed measured at 1.95% (1.40–2.51), from 47 cases, ahead of Golden Retrievers at 1.39% and Weimaraners at 0.85%. In a case-control analysis of those 453 cases against 2,036 controls, the Boxer’s odds ran 10.7 times those of crossbred dogs (3.7–30.4). Median age at diagnosis across all breeds was 8.2 years, with the middle half between 6.0 and 10.2. Any new lump on a Boxer gets looked at, not watched.
Lymphoma. A European network compared 1,529 lymphoma cases against 55,529 controls across eight countries. Boxers supplied 88 cases, 5.1%, the second most represented breed. The study’s own headline is that risk differed by country. Boxers were “highly predisposed only in France (OR = 6.89)”, with milder odds in Italy (2.92) and the UK (2.56). Type was more consistent: Boxers came out predisposed to high-grade T-cell lymphoma at 10.9 times the odds of crossbreeds.
The brain. Brain disorder was the third most common cause of Boxer death in the UK records, at 33 of 346, 9.54%. A comparative review of canine brain tumours reports that gliomas are “highly overrepresented in several brachycephalic breeds including boxers”, and that meningiomas are overrepresented in the breed as well. That review gives no odds ratio and no denominator, so treat the direction as established and the size as not.
The DM result that looks like a catastrophe and is not one
OFA holds 6,131 Boxer DNA results for degenerative myelopathy: 20.9% clear, 29.6% carrying one copy, and 49.5% carrying two. Third highest of any breed.
Read that carefully. It is a genotype, not a diagnosis. The variant sits in a gene called SOD1. OMIA records the inheritance as recessive, then adds that “some homozygous mutant dogs had no signs of degenerative myelopathy, which suggests incomplete penetrance or other causative loci.” In plain terms, two copies raises the risk by an amount nobody has pinned down.
So how many do? We could not find a published figure, and we looked. No study we could open has followed a group of two-copy Boxers to the end of their lives and counted. Saying that half of all Boxers have a spinal cord disease would be false. Saying that half carry a risk marker of unknown strength is what the evidence supports.
What the result is genuinely useful for is breeding. Two carriers bred together is how a two-copy puppy arrives, and a cheek swab settles it. The breed club lists the DNA test as recommended, once.
Thyroid, and a category most owners never hear about
OFA’s thyroid registry holds 2,328 Boxer results: 75.4% normal, 10.4% abnormal and 14.1% equivocal, which ranks the breed ninth. Note which number is bigger. More Boxers landed in the middle category than in the abnormal one.
Equivocal is not a mild version of abnormal. OFA defines it as dogs “with laboratory results that are questionable, therefore not definitive”, and asks for a retest in three to six months. The panel measures three things at once: a thyroid hormone, the pituitary signal telling the gland to work harder, and an antibody against thyroid protein. Those three can disagree. The registry also warns that “a negative at any one time will not guarantee that the dog will not develop thyroiditis”, which is why it asks for rechecks at 2, 3, 4, 6 and 8 years.
Actual illness is rarer than either figure suggests. In the UK vet records, hypothyroidism was diagnosed in 54 of 3,219 Boxers, 1.68%, in a year.
Joints, breathing and white coats
Hips and elbows are the good news. OFA graded 7,703 Boxer hips and found 12.7% dysplastic, which places the breed 99th of 219 ranked breeds, mid-table. Elbows are better still: 1.1% abnormal of 1,780, ranking 141st. Two cautions come with any registry figure. Normal hips are 8.2 times as likely to be submitted as abnormal ones, so read 12.7% as a floor. And dysplasia is graded on a film. A dog can be graded dysplastic and never limp.
Breathing. Boxers are brachycephalic (flat-faced), and the standard makes it official, asking for a muzzle “⅓ the length of the head from the occiput to the tip of the nose”. But the honest comparison with the Bulldog and the French Bulldog is not close. In 2026 Cambridge researchers graded 898 dogs across fourteen flat-faced breeds on an exercise test, counting grades II and III as clinically significant. The 79 Boxers were among the breeds where at least half scored a clean grade 0 and at least three quarters were clinically unaffected. On the same grading system, 604 dogs of the three worst-affected breeds came out at 64.6% affected for 189 Pugs, 58.9% for 214 French Bulldogs and 51.2% for 201 Bulldogs.
That is a real difference, not a rounding error. It is not a clean bill of health either: up to a quarter of those Boxers were not clinically clear. There is now a scheme to ask about, too. In April 2026, citing the Cambridge work above, OFA added the breed to the list eligible for both the respiratory grading exam and an official certificate.
One honest wrinkle: further down that same OFA page sits an older line saying the programme “is currently open to Pugs, Bulldogs, and French Bulldogs.” Both sentences are live at once. We take the April 2026 update as the current position because it is the newer of the two, and we mention the other because you may find it and wonder.
Either way it is new, so no registry percentage has built up for this breed yet. A grade on one dog is still something a breeder can hand you.
White Boxers. About one in ten Boxers is white, and the breed standard disqualifies “Boxers with a total of white markings exceeding one-third of the entire coat” from the show ring. On health, the UK records are reassuring and thin at the same time. Of the 34 most common disorders in 3,219 Boxers, none differed in prevalence between white and non-white dogs, and median lifespan was the same. Deafness is the exception that the study could not test: only two Boxers in the entire dataset had deafness recorded, one white and one not. The standard reference on inherited deafness states there is “a high prevalence of deafness in white boxers” but attaches no number to it, and the genetic study it cites did not assess hearing at all. If you are buying a white puppy, ask for a BAER hearing test.
Eyes. Corneal ulceration was recorded in 161 of 3,219 Boxers, 5.00%, in one year. That is the third most common thing written into a Boxer’s notes, and worth knowing before you dismiss a watery eye.
How long they live
Two UK primary-care studies agree closely. The larger one recorded 346 Boxer deaths at a median of 10.46 years, with the middle half between 9.00 and 11.98. An earlier study of the same kind of data found 91 Boxer deaths at a median of 10.0 years, middle half 7.7 to 11.6, against 12.0 years for dogs of every breed in that same dataset. So roughly two years short, measured inside one population rather than stitched between two.
For context, the largest UK life-table study to date puts dogs generally at 12.5 years across 584,734 animals. It does not name this breed anywhere in its main text.
What we could not verify
How many Boxers actually get ARVC. No study has counted it across the breed. The 23% figure above is the share of clinically normal Boxers crossing a Holter threshold, which is not the same question.
How many two-copy Boxers develop degenerative myelopathy. Nobody has published it. Anyone quoting a penetrance percentage for this test is quoting something we could not find.
This breed’s row in the 2024 life-table paper. It sits in a supplementary file we could not open, so we used the primary-care figures and said which.
A month-by-month Boxer puppy weight chart. The ones in circulation cite nothing. Ours is a model fitted to adult weights, and a Boxer sits inside the range it was validated on, but it is still a prediction.
Any daily exercise figure. Not in the standard, not in any study we could open. Watch the dog, not the clock.
A registry breathing figure for the breed. OFA only opened certification to Boxers in April 2026, so nothing has accumulated to quote yet. Ask a breeder for the grade on the individual dog instead.
Anything about children. No study grades any breed for this, here or anywhere else on this site.