The objective of this study was to determine the prevalence of canine herpesvirus 1 (CHV1) in breeding bitches on Belgian kennels and to relate this to fertility problems and/or neonatal death. By using a seroneutralisation test with complement to detect anti-CHV1 antibodies, a prevalence of 49.5% was found in a population of 97 breeding bitches in 18 kennels. In nine kennels, all examined breeding bitches were negative. In the other nine kennels 2/3 to all of the examined breeding bitches were positive. In seven kennels with positive breeding bitches serious problems were observed concerning neonatal death and/or infertility, whereas only one kennel with negative breeding bitches had problems with infertility, which indicates that there is a relation between the presence of positive breeding bitches and neonatal death and/or infertility in the kennel. This relation was also observed on animal level. 76% of the bitches that had recently lost a litter before the age of 3 weeks and57% of the bitches with fertility problems were positive. In contrast, only 33% of the “problem-free” bitches were positive. It was concluded that CHV1 is kennel-related and that kennels, where the virus is enzootically present, experience neonatal death and infertility more frequently.