Nevirapine has several properties that make it an attractive candidate for antiretroviral therapy to interrupt HIV-1 transmission in the intrapartum and early postpartum period. The pharmacokinetic profile suggested that nevirapine would be rapidly absorbed and transferred to the infant in utero when given during labor and delivery. In addition, nevirapine has been shown to penetrate cell-free virions and inactivate virion-associated reverse transcriptase (RT) in situ. This property would be potentially useful in inactivating cell-free virions in the genital tract as well as in breast milk. These characteristics of nevirapine suggest that treatment of an HIV-infected pregnant woman in labor with an oral dose of nevirapine may provide a prophylactic level of nevirapine in the infant during the time of exposure to virus in the birth canal and/or maternal blood. In addition, nevirapine may inactivate the virion-associated RT present in cell-free virions in the genital tract or breast milk.