An acute outbreak of reproductive failure associated with porcine parvovirus (PPV) infection occurred in a swine herd with a group-farrowing system. In Group A, of 35 bred females, 17 (49%) farrowed. Mummification was the predominant sign, increasing from an endemic level of 0.22 per litter in previous farrowing groups to 4.10. Diagnosis of PPV was made from abnormal fetuses in Group A. In the next group (Group B), only 8 of 35 (23%) females bred and farrowed, and they averaged 0.25 mummified fetuses per litter. Remaining sows did not farrow as scheduled and indicated a high incidence of early embryonic resorption. In Group C, 19 females farrowed out of 35 bred (54%), and averaged 0.32 mummified fetuses per litter. Clinical patterns and size of mummified fetuses suggested that PPV infection occurred in Group A during the second third of pregnancy, in Group B during the first third and in Group C prior to mating. An estimation of the net opportunity cost experienced due to this outbreak ($7260.000) is made to emphasize the importance of instituting and maintaining an effective preventive medicine program.