Abstract: A method for quantitative determination of new nonmercurial diuretic chlorothiazide—— 6-chloro-7-sulfamyl-1,2,4-benzothiadiazine-1,1-dioxide is proposed.It is based on titrations of this compound in two kinds of nonaqueous solvents:ethylenediamine and acetone. Either pure compound or tablet of chlorothiazide can be satisfactorily titrated in ethylene- diamine using o-nitroaniline as indicator,when standard solution of potassium hydroxide in isopropyl alcohol is used as titrant.On the other hand,a very sharp end point can also be obtained in acetone using azo violet as indicator,but the end point is not very stable. During potentiometric titration in acetone with the use of antimony-calomel electrodes,a clear inflection appears,which coincides with the color change of indicator.