In a recent study, Kalz and Scott 1 investigated some of the cutaneous changes during the menstrual cycle. They found that the skin, similarly to other body tissues, took on added water during the premenstrual period. On the basis of this finding, they employed an oral diuretic premenstrually in a series of patients with acne. The active ingredient of the diuretic was ammonium chloride, and the average daily dose was about 2 gm. They reported that this medication had a moderately good supressing effect on the premenstrual flare-ups of acne. More recently, chlorothiazide (Diuril) has become available for clinical use. This drug is an exceptionally potent, orally effective, nonmercurial diuretic agent. 2 Accordingly, chlorothiazide was administered to a group of 20 patients who had severe premenstrual flare-ups of their acne. Most of these patients previously had been given conjugated estrogenic substances (Premarin) during the last