Ten patients with severe congestive heart failure (6 women and 4 men, aged 67 +/- 4.35 years) were given diuretic therapy with either furosemide or metolazone followed by combined therapy of both agents. We found that the furosemide-metolazone combination induced greater natriuresis, urinary output and weight loss than did furosemide or metolazone alone. Notably, none of our patients displayed profound diuresis, severe hyponatremia or deterioration of renal function, found previously in high-risk patients treated with this combination.