It is remarkable that in spite of a rather frightening list of side-effects, therapy with corticosteroids is being advocated in a widening variety of diseases. In recent years the use of corticoids in advanced mammary cancer has been reported, and the term medical adrenalectomy is becoming increasingly fashionable. While the role of as against hypophysectomy, in this disease is still being hotly debated, the role of corticosteroid therapy has not been clarified. The papers published to date on this subject are on small series, and do not agree on such vital points as the proportion of cases responding, the most effective compounds, the optimal dose level, and the relationship between benefit from corticosteroids and tjiat from sex-hormone manipulation or adrenalectomy. Of critical importance also, but so far unestablished, is the selection of cases likely to respond to such therapy, and the possible additive effect of other agents given concurrently. Since cortisone administration leads to atrophy of the adrenal cortex, its use in cancer of the breast has been loosely referred to as a medical adrenalectomy, and varying degrees of benefit have been claimed in a number of reports (West et al., 1954; Pearson et al., 1955; Lemon and Reynolds, 1956; Read, 1957; Kolodziejska, 1959). At one extreme it has been suggested that cortisone is as effective as either adrenalectomy plus oophorectomy, or hypophysectomy, both in survival and objective remission rate (Lemon, 1961). At the other extreme it has been graphically stated that corticosteroids merely allow the breast-cancer patient to walk to the necropsy room (G. Escher, personal communication, 1960). In recent years several trials of prednisolone in breast cancer have been reported (Kennedy,1957; Kofman et al., 1957; Lemon, 1959; Gardner et al., 1962). I have pre viously reported trials of prednisolone combined with nitromin (nitrogen mustard oxide) (Stoll, 1960a), and also of dexamethasone (9a-fluoro-166a-methyl-prednisolone) administration in breast cancer (Stoll, 1960b).