Pregnant women in active labor receive single doses of oral nevirapine. The neonates of the first 4-6 (PER AMENDMENT 8/27/96, was 4) mothers receive no drug, while the neonates of the second 4-6 (PER AMENDMENT 8/27/96, was 4) patient cohort receive a single dose of nevirapine. If neonatal antiviral levels of nevirapine are not sustained for 7 days after the single dose, a third cohort of 4-6 (PER AMENDMENT 8/27/96, was 4) pregnant women will receive a single dose of nevirapine and their neonates will receive multiple doses of nevirapine to maintain an antiviral effect for 7 days.