Three women presented with acute primary herpetic gingivostomatitis during the first half of their pregnancy. Herpes simplex virus (HSV) was isolated by culture from the buccal lesions in two cases, and a serological confirmation of primary HSV infection was evident in the third case. One fetus, delivered during the second trimester of pregnancy, had a central nervous system anomaly, which was probably not related to the infection. The placenta exhibited mild diffuse deciduitis and focal villitis. The other two fetuses were normal and born at term. Microscopic examination of the placentas and membranes disclosed deciduitis and basal placentitis in one, which may have been caused by the herpes virus. The literature on intrauterine infection with HSV is reviewed, focusing on the significance of Type I virus as a possible teratogen. At present, there seems to be insufficient evidence to indicate pregnancy interruption following nongenital primary HSV infection in early pregnancy.