Gilts vaccinated IM either once (4 gilts) or twice (2 gilts) with an acetylethyleneimine-inactivated porcine parvovirus (PPV) vaccine before they were bred were subsequently exposed intranasally and orally to virulent PPV at about the 40th day of gestation (from 37 to 43 days). At 2 weeks after vaccination, all had hemagglutination-inhibiting (HI) titers for PPV (from 20 to 80) which decreased by the time the immunity was challenged with virulent virus (from 10 to 40), but increased thereafter (from 160 to 1,280). Titers of singly and doubly vaccinated gilts were similar throughout the experiment. The gilts were killed at about the 84th day of gestation (from 80 to 87 days), and their litters were examined. Litters were comprised of 68 live fetuses and 1 dead fetus (7 to 14 fetuses/litter). Neither viral antigen, PPV, nor homologous HI antibody was found in any of the fetuses. In addition, 4 gilts were kept in contact with the vaccinated gilts and were treated similarly except for vaccination. These 4 gilts remained free of HI antibody until after they were exposed to virulent PPV during gestation. At the time the gilts were killed the titers were 1,280 to 2,560. Their litters were comprised of 11 live fetuses and 26 dead fetuses (8 to 11 fetuses/litter). Virus was isolated from fetuses of all litters. Viral antigen was found in 24 of the dead fetuses and 10 of the live fetuses. All infected live fetuses also had HI antibody for PPV. The 2 boars used to breed vaccinated and nonvaccinated gilts (usually each gilt was bred to each of the 2 boars), but not exposed to virulent PPV, remained free of HI antibody for PPV.