In a series of 32 fetuses and neonates studied at autopsy at Women and Infants Hospital, group B streptococcus (GBS) was isolated from the right atrial blood or from the lung. Eleven or 34% (5 stillborn fetuses and 6 liveborn infants) were delivered in midgestation, between 18 and 28 weeks, and all weighed less than 1000 g. Maternal clinical features in GBS infection during midgestation included vaginal hemorrhage in 4 and premature rupture of membranes in 8. The high rate of fetal death associated with this infection in midgestation (45%) bears emphasizing. Reproductive loss among mothers with previous pregnancies seems to be a risk factor for subsequent perinatal loss due to GBS. Of 17 pregnancies among these 11 mothers, only 3 resulted in living children. Colonized mothers with GBS are usually treated late in the third trimester, if at all. This study indicates that attention must be directed to midgestation, at least among the high-risk group.