Chlorothiazide (Diuril) is an orally administered, nonmercurial, diuretic agent. Chemically, it is known as 6-chloro-7-sulfamyl-1,2,4-benzothiadiazine-1,1-dioxide. 1 It was made available commercially only this year; but, in its use thus far reported, the absence of toxic and otherwise undesirable side-effects has been especially noted. 2 Ten of 51 patients observed by Hollander and Wilkins 2a experienced slight to moderate weakness and fatigability, which usually disappeared with continuous treatment. In several, this weakness was associated with a feeling of mental depression, and, in a few of these, the level of serum potassium was reduced. Five patients complained of temporary mild nausea, especially when given 500 mg. of chlorothiazide in single doses. Other uncommon side-reactions included muscle cramps, flushing, lightheadedness, and paresthesias. The potential development of clinical symptoms and signs of fluid and electrolyte imbalance resulting from chlorothiazide therapy has been stressed by all investigators. 2 So far as we know, purpura resulting