In a double-blind dose-response study, 49 patients with New York Heart Association functional class III or IV heart failure were randomized to receive a single intravenous dose of 5, 10, or 20 mg torsemide or 40 mg furosemide. Torsemide produced dose-related decreases in body weight and increases in sodium and chloride excretion and urine volume. With the 20 mg dose of torsemide and the 40 mg dose of furosemide, body weight decreased significantly relative to baseline, and total and fractional 24-hour urinary excretion of sodium, chloride, and potassium and urine volume increased significantly. The 10 mg torsemide dose also produced a significant increase in urine volume. The results indicate that intravenous torsemide is effective for the acute treatment of sodium and fluid retention resulting from moderate to severe congestive heart failure.