In spite of a very recent upsurge in breast-feeding in industrialized countries, approximately one-half of parturients are candidates for postpartum lactation suppression. The mechanisms controlling lactation are complex and involve preparation of the breast during pregnancy, stimulation of secretion of milk in the immediate postpartum period, ejection of milk from the alveolar cells, and maintenance of milk production during the period od lactation. The local effects of estrogen and progesterone in the breast prevent milk secretion during pregnancy. With their withdrawal in the postpartum period, the stimulating effect of the anterior pituitary hormone prolactin dominates and milk secretion is initiated and maintained. Milk ejection is accomplished by a neurohormonal reflex resulting in stimulation of the myoepithelial cells of the breast by the posterior pituitary hormone oxytocin. Local stimulation of the breast by suckling is important in initiating the release of oxytocin and also the secretion of prolactin. The suppression of lactation in the postpartum period can be accomplished in approximately 60--70% of females by the use of a tight brassiere and avoidance of stimulation of the nipples. An additional 10% or so of females can be helped with the use of estrogens during the postpartum period. The addition of an androgen to the estrogen increases the success rate of lactation suppression to about 90%. Unfortunately, the use of estrogen alone or in combination with an androgen is accompanied by rebound lactation in a significant number of patients and has been associated with an increased incidence of postpartum thromboembolic disease. Lactation suppression by inhibiting prolactin secretion with synthetic ergot alkaloids such as bromocriptine has been shown to be safe and highly effective both immediately post partum and after lactation has been established. The 2 week period of therapy required with this drug may be unsatisfactory for some patients. If given immediately at delivery, a single injection of testosterone enanthate and estradiol valerate is equally effective in suppressing lactation and, in the young patient who has delivered vaginally, is not associated with significant risk.