In a double-blind study vs bromocriptine, 30 women who wished to interrupt breast-feeding after a physiological delivery and at least 3 months of nursing were given at random 10 mg dihydroergocristine capsules or 2.5 mg bromocriptine capsules twice a day for 5 days, then 3 times a day for 5 days if treatment had failed to produce an effect. The parameters considered were PRL plasma levels, which were measured at baseline, on the 5th day and, where necessary, on the 10th day of treatment. Milk secretion, breast swelling and pain were recorded at baseline and daily during treatment. The appearance of any side-effect was accurately reported. A prolactin decrease was observed in both groups (p less than 0.01). After 5 days milk secretion was reduced more significantly in the dihydroergocristine group; after 10 days of treatment 6 cases treated with bromocriptine and 1 case treated with dihydroergocristine still revealed a low milk secretion. Breast congestion and pain were absent in both groups. As regards side-effects, a significant decrease in systolic blood pressure (standing position) was reported in the bromocriptine group. Other symptoms, such as nausea, vomiting, insomnia and headache, were reported in 8 patients in the bromocriptine group vs 6 patients in the dihydroergocristine group.