Ten patients with chronic renal failure from different genesis (serum creatinine levels 150-200 mumol/l), were evaluated from the aspect of the effect of the diuretic therapy. The effects of furosemide (FUR) and polythiazide (POL) were assessed after 3-month application. The mean values of the estimated parameters before treatment, after 3-month administration of FUR as a monotherapy and after the next 3 months simultaneously used (FUR + POL), presented a stable increase of the diuresis, without statistically significant changes of the global renal function, and triglyceride disorders. On the contrary, the improvement of calciuria through combined using of furosemide and polythiazide is statistically and clinically significant.