In July of 1994 an acute onset of maternal reproductive failure occurred in a 2,330 sow farrow-to-finish farm. Clinical signs observed in the affected sows were typical for porcine reproductive and respiratory syndrome (PRRS). During the first 6 weeks of the epizootic 1,117 sows farrowed; 216 (19.33%) farrowed before the 110th day of gestation. The majority of piglets born before term died within a few days of birth and the mortality rate for term piglets increased to a maximum of 75.56% during the 5th week of the epizootic when 1,562 out of 2,067 piglets were either born dead or died prior to weaning. Preweaning mortality rates gradually returned to normal values within 16 weeks. The incidence of respiratory disease in the weaned and fattening pigs increased during this time. Although specific prophylactics against respiratory diseases were administered, the death rate doubled for the weaned and fattening pigs.