Six serologically negative sows were infected by intranasal instillation of porcinecytomegalovirus (PCMV) between 31 and 85 days of pregnancy. Four sows showedan afebrile anorexia and lethargy 14-25 days after infection and all 6 developedsignificant increases in indirect immunofluorescent (IIF) antibody titres within35 days. Virus was recovered from nasal and/or cervical swabs from 2 sowsduring life and from lung macrophage cultures after death.At term the sows were killed and their fetuses harvested by caesarean section.The number of mummified and stillborn fetuses increased from 4/63 in 6 previouslitters to 18/60 in the 6 present litters. Nine of 43 fetuses born alive were rearedin isolators for up to 6 weeks but the majority were killed for examination on theday of birth. Virus was isolated from 16 piglets from 4 of the 6 litters examined;it was isolated most frequently from lungs and liver but also from spleen, kidney,brain and nasal mucosa. Unsuckled day-old pigs had insignificant IIF titres,irrespective of whether they were excreting virus or not. The 5 congenital excretorswhich were reared all died within 7 days but no deaths occurred among their 4litter-mates. Post-natal infection of 2 of these piglets reared in contact withcongenitally infected pigs was suggested by the recovery of virus from nasal swabs17 and 27 days after birth and the subsequent rise in IIF titre to 1/256 by day 42.