The aim of this article was to present results of the study on the quantitative determination of antibodies anti-CPV-1 and anti-FPV in vaccinated and nonvaccinated dogs and cats, respectively, and to establish whether vaccination stimulated protective immunity against these diseases in both animal species. In the group of dogs vaccinated against parvovirosis, high titres of antibodies to CPV-1 were found in 86.7%, and low titres in 13.3% of animals. In the group of non-vaccinated dogs low titres of antibodies were recorded in 30%, and high titres in 70% of animals. In the group of cats nonvaccinated against panleukopenia, mean titre of antibodies to FPV was recorded in 20% and high titre in 80% of animals. All cats vaccinated against panleukopenia had high titres of FCV antibodies. Results from this study have indicated widespread contamination of the environment with CPV i FPV and have confirmed that immunization against feline paleukopenia and canine parvovirosis induced protective immunity in both species. They have also indicated that serological tests are a valuable tool in assessing the epizootic situation and moreover, they can be used to determine the efficacy of vaccination, as well as the optimal vaccination date.