The short-term clinical efficacies of furosemide, 25 mg/day, and torasemide, 10 mg/day, have been compared in 2 groups of 12 patients with severe heart failure. In each group there were similar numbers of patients in whom heart failure was due to coronary heart disease, high blood pressure, or idiopathic dilated cardiac myopathy. The design of the study was open and the diuretics were added to baseline treatment with digoxin. Treatment for 8 days with the 2 loop diuretics resulted in similar substantial and significant improvements in symptoms and exercise tolerance as judged by the increase in total body oxygen consumption, and reductions in radiographic evidence of pulmonary congestion and in right heart filling pressure as judged from the jugular venous pressure wave. The results of this short-term comparative study confirm that furosemide and torasemide are equally efficacious in inducing substantial improvements in the clinical status of patients in severe heart failure.