Since it has been clearly established that multiple drug chemotherapy is more effective than the use of a single drug for advanced carcinoma of the breast, the latter is not commonly used today. However, upon failure of one of two combinations of drugs, if any of these drugs are then tried singly they are rarely useful, and valuable time is lost. It is at this point that megestrol acetate, a potent progestin, was found to be effective in 30 per cent of a series of 161 patients with advanced carcinoma of the breast. This drug was given orally, 40 milligrams, after each meal and at bedtime, without any toxicity or any undesirable reactions, except a weight gain--not fluid retention--in patients less than 55 years of age. The average duration of response was 8.1 months from onset of megestrol acetate therapy and for the group classified as unchanged, 5.2 months. This drug is at least as effective as any steroid or cytotoxic compound but has the advantage of not producing toxicity and, with the exception of weight gain in patients less than 55 years, no undesirable reactions of any kind, such as bone marrow depression, alopecia, nausea, vomiting or diarrhea. Hence, it can be properly administered by the patient's physician or surgeon. Since oncologists known that medroxyprogesterone therapy had not shown promising use for advanced carcinoma of the breast, it was assumed that megestrol acetate also had little activity, and hence, it was not used. However, those who did give it a trial found it a valuable compound in the management of advanced carcinoma of the breast, even after failure of all hormonal or cytotoxic combination trials. It proved to serve as an important addition to our armamentarium in the management of advanced carcinoma of the breast.