Cytomegalovirus is the most common cause of congenital and perinatal viral infections throughout the world. Congenital infection occurs in 1% of all live births in developed countries and in an even higher percentage in developing nations. As a result of transmission during birth, by breast milk, and by blood transfusions, perinatal infections are much more prevalent than congenital infections. The vast majority of these infections are chronic, subclinical forms, but symptomatic infections are sufficiently prevalent and dangerous to represent a major unsolved public health problem throughout the world. In this review the epidemiologic, clinical, immunologic, and therapeutic facets of cytomegaloviral infections in pregnant women and their offspring will be discussed. © 1990, University of Chicago.