An unexpected 20-week-old pregnancy was found in a young acromegalic who had been treated with 10 mg bromocriptine/day for 10 months. The drug was continued throughout the period of gestation. No growth of the pituitary adenoma was noticed. The intrauterine development of the fetus was normal. Bromocriptine therapy had no discernible effect on the expected patterns of secretion of placental hormones, but inhibited completely the increase of PRL in the serum of the mother. Maternal plasma GH concentrations were very high in spite of the treatment and progressively declined after delivery. The plasma GH level was normal in the child, but PRL was very low at birth and increased in the following days. The expected high PRL concentration was found in the amniotic fluid. This case study suggests that bromocriptine crosses the human placenta and affects the fetal pituitary, maternal GH does not influence fetal or amniotic GH, and amniotic fluid PRL correlates poorly with either maternal or fetal blood levels and is not affected by bromocriptine.