Porcine reproductive and respiratory syndrome virus(PRRSV)0, porcine circovirus type 2(PCV-2) and porcine parvovirus (PPV)0 infections were investigated as possible causes of the postweaning multisystemic wasting syndrome(PMWS). Specific primers for RT-PCR and PCR were designed for the differential detection of PRRSV, PCV-2 and PPV. Using PCR, these viruses were detected in homogenized tissue samples from pigs that had respiratory of reproductive problems in the time period between 1998 and 2000; the overall prevalences were: PRRSV 31.4%, PCV-2 46.5%, and PPV 8.1%. PCV-2 was also detected in aborted fetal tissues.