NVP 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 suggests that NVP would be rapidly absorbed by the mother and transferred to the infant in utero when given during labor and delivery. The HIV-1 antiviral activity is rapid with significant reduction in plasma virus occurring within a few days of drug administration. In addition, NVP 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 NVP suggest that treatment of an HIV-infected pregnant woman in labor with an oral dose of NVP may provide a prophylactic level of NVP in the infant during the time of exposure to virus in the birth canal and/or in the maternal blood. In addition, NVP may inactivate the virion-associated RT present in cell-free virions in the genital tract or breast milk.