A serosurvey for viruses associated with reproductive disorders was conducted in 25 conventional Belgianfarms. Serum antibody titers for porcine reproductive and respiratory syndrome virus (PRRSV), porcinecircovirus type 2 (PCV2), porcine parvovirus (PPV), porcine enteroviruses (PEV) and swine influenza viruses(SIV) were determined in gilts and sows. All the animals were seropositive for PCV2 and >95% wereseropositive for all 4 embryopathogenic PEV serotypes. Consequently, special preventive measures appear tobe unnecessary for these viruses. In 1 farm, non-vaccinated gilts were found to run a risk of developing PPVinducedreproductive disorders. Vaccination against PPV could exclude this risk. In 10 farms, gilts seronegativefor one or more specific SIV subtypes were introduced into a herd that had previously been infected with thesame subtypes. Vaccination of gilts against SIV may prevent reproductive disorders in gilts and respiratoryproblems in their offspring. In 1 farm, newly purchased gilts that were possibly shedding PRRSV wereintroduced into a PRRSV seronegative sow herd. Serological screening prior to purchase or vaccination of thesows could have resolved this dangerous situation.