Boars may play a significant role in dissemination of parvovirus (PPV). During acute infection the virus is shed by various routes, including semen. The objective of this study was to evaluate occurrence of natural infection with porcine parvovirus in boars in the Czech Republic by serological examination. A total number of 800 sera from boars of 42 herds were collected. The sampling was made between January and December 1999. All serum samples were tested for porcine parvovirus (PPV) antibodies by haemagglutination inhibition test (HIT). In 31 herds, boars have never been vaccinated to PPV. In 11 herds boars were regularly vaccinated to PPV. A pig was considered infected with HI titres higher than 1:256 in non-vaccinated herds. In vaccinated herds non-infected boars could be determined only with titres equal to or lower than 1: 256. Infection with porcine parvovirus was detected in 80.6% of non-vaccinated herds. Non-infected boars were only found in 18.2% of vaccinated herds. From the total number of 528 boars tested in nonvaccinated herds 60.8% were detected as infected. From the total number of 272 boars tested in vaccinated herds 37.5% were found to be non-infected. Our results indicate that infection with porcine parvovirus is widespread in boars in the Czech Republic. With regard to the possibility of excretion of parvovirus in semen it is obvious that boars can play an important role in transmission of parvovirus in pig herds in the Czech Republic.