A nursing mother was given haloperidol 5 mg twice daily for puerperal psychosis and continued to breast feed under hospital supervision. Despite considerable amounts of haloperidol being secreted in the breast milk (up to 23.5 micrograms/l), the infant was apparently not sedated, fed well, and continued to thrive. The findings suggest that maternal ingestion of haloperidol for short periods has no deleterious effect on the infant's development.