Because of their ambidextrous qualities—being useful both as diuretic and as antihypertensive agents—the drugs chlorothiazide and hydrochlorothiazide have, within the past two years, come to enjoy a tremendous use in situations ranging from the treatment of the most severe cases of cardiac insufficiency and essential vascular hypertension to their questionable use in eliminating water from fat persons for purposes of weight reduction. There have been scattered reports in the literature which have mentioned the development of purpura in patients receiving these drugs. In some instances, this purpura has been stated to be accompanied by platelet deficits and in other instances, to be associated with normal platelet counts. Jaffe and Kierland1 reported two such cases of purpura. In the first case, it was stated that the bleeding and clotting times and other results of hematological tests were normal. In the second case, the platelet count was 94,000 per cubic millimeter.