A former heroin addict treated with methadone maintenance throughout pregnancy, with rapid dose reduction from 110 mg to 9 mg during the last five weeks pre-partum, was evaluated in late pregnancy, at time of labor and delivery, and post-partum; her child was also evaluated. Using gas and thin-layer chromatography and mass spectroscopy, methadone levels were measured, and other drugs looked for in (1) plasma during late pregnancy, (2) mixed cord blood, (3) amniotic fluid at delivery, (4) maternal plasma and milk post-partum (on 50 mg methadone), (5) neonatal plasma and urine. Low levels of methadone were present in amniotic fluid and neonatal urine but not in mixed cord blood or neonatal plasma. Levels of methadone present in breast milk during moderate dose maintenance were also low. Unexpectedly, pentobarbital was identified in amniotic fluid. Neonatal infection was also diagnosed. Multiple factors may have contributed to symtoms observed in the neonate.