The effect of oral administration of sulpiride isomers on PRL secretion and breast engorgement was studied in 60 multiparous nursing mothers, according to a double blind schedule: 45 women were orally given 50 mg sulpiride (L, D, L-D form) twice daily during the first 5 days of puerperium, 15 were given a placebo in the same way. Basal, the 3rd and 5th day serum PRL levels were determined and every day milk secretion was evaluated. On milk samples obtained on the 5th day, sulpiride concentration was measured. 40 women with insufficient lactation and 20 with total lack of milk, 25-40 days after delivery, were treated in the same way, in double blind. Milk secretion was evaluated at the beginning and at the 5th, 10th and 15th day. The mean total milk yield (± S.D.) during the first 5 postpartum days in sulpiride groups were significantly greater than that in the control group. Plasma PRL levels resulted significantly higher in sulpiride treated groups than in placebo group. All women with insufficient or absent milk secretion could avoid supplemental bottle-feeding after 10 days of treatment.