This paper presents puppy mortality and postmortem findings for a birth cohort of boxer puppies born in the Netherlands between January 1994 and March 1995. In all, 457 litters were registered, of which 414 (90.6 per cent) were involved in the study. The 414 litters contained 2629 puppies, a mean litter size of 6.4 puppies. Of the 2629 puppies 571 (21.7 per cent) died or were euthanased before they were weaned at 50 days of age; there were 147 (25.7 per cent) stillbirths; 102 (17.9 per cent) were euthanased because they were white; 269 (47.1 per cent) of the puppies died during the first 21 days of life and 53 (9.3 per cent) puppies died between days 22 and 50. The cause of death or the reason for euthanasia was assessed by either the breeder or the veterinarian in 176 of these 269 puppies but was not determined in the other 93 puppies. Three hundred and two puppies were examined postmortem; the most important causes of death or reasons for euthanasia were inflammatory disorders (102; 33.8 per cent), non-inflammatory disorders such as asphyxia and malnutrition (66; 21.9 per cent), euthanasia because they were white (51; 16.9 per cent), and congenital abnormalities (45; 14.9 per cent). No cause of death or reason for euthanasia could be found for 38 puppies (12.6 per cent).