In 414 pregnant women with a history of recurrent genital herpes simplex infection, we studied the correlation between asymptomatic viral shedding in late pregnancy and at the time of delivery. Antepartum cultures for asymptomatic reactivation of herpes simplex virus were positive in 17 of the 414 women (4.1 percent). None of these women had positive cultures at the time of delivery. Cultures of specimens obtained at delivery from 5 of 354 asymptomatic mother-infant pairs (1.4 percent) were positive for asymptomatic excretion of herpes simplex virus. None of these women had had antepartum cultures that documented asymptomatic excretion of herpes simplex virus, despite the fact that culturing was repeatedly performed during the four weeks before delivery. Asymptomatic shedding of herpes simplex virus occurred with the same frequency at delivery, whether or not any episodes of symptomatic recurrence were noted during the pregnancy (1.4 vs. 1.3 percent). We conclude that antepartum maternal cultures do not predict the infant's risk of exposure to herpes simplex virus at delivery.