PIP: The use of megestrol acetate in treatment of malignancy (endometrial carcinoma, ovarian cancer, prostate cancer, breast cancer, renal cell carcinoma, malignant melanoma), endometrial hyperplasia, benign prostatic hypertrophy, contraception, anorexia, cachexia and weight loss is reviewed, concluding with a toxicity profile. Megestrol acetate was introduced in 1971 for treatment of endometrial carcinoma. Megestrol acetate is probably effective in proportion to the number of cytoplasmic progesterone receptors, but it has not been tested in a Phase III trial. For ovarian cancer it has been reported to be effective in 1 trail at doses of 800 mg/day. Prostate cancer, although difficult to assess, responds to megestrol acetate at doses of 120 mg/day because of its suppression of gonadotropins, its inhibition of 5alpha-reductase and its binding to the dihydrotestosterone receptor. Megestrol acetate permits a lower dose of diethylstilbestrol, and thus lower toxicity. There is apparently a dose-response between megestrol acetate and breast cancer, along with a response dependent on the number and type of estrogen and progestin receptors. Responses are better in postmenopausal women, and additive with other agents such as tamoxifen and mitomycin C. The medium duration of effect is 6-8 months. It has no effect on renal cancer or malignant melanoma. Megestrol acetate can be considered as an effective medical alternative to surgery for endometrial hyperplasia or benign prostatic hypertrophy. As a contraceptive in inhibits sperm transport rather than ovulation, but also causes irregular bleeding. Megestrol acetate has few side effects, and has the advantage of stimulating appetite and weight gain, a benefit in cancer patients.