Decapeptyl (D-TRP-6), a potent luteinizing hormone-releasing hormone analogue, was administered to 27 premenopausal women with advanced breast cancer; patients were known to have hormone receptor-positive tumors. An overall response rate of 70% was achieved (complete response = 18%, partial response = 52%), with a median time to progression for the whole patient population of 12 months. Toxicity of the schedule was restricted to hot flushes, and the use of a 4-week initial covering period of tamoxifen prevented any flare-up of disease activity from occurring.