A clinical trial was conducted in open, randomized, parallel fashion to determine the effectiveness and safety of bumetanide compared with those of furosemide in 42 outpatients with edema due to congestive heart failure. All patients were free from any significant hepatic or renal disease. The duration of the study was six months, except for 12 patients who were continued under treatment with bumetanide for an additional six months. Changes in body weight, edema, abdominal girth, hepatomegaly and other signs of congestive heart failure were evaluated. No statistically significant differences between bumetanide and furosemide were noted in these clinical parameters. Blood pressure was decreased in both groups, more consistently with furosemide, but without statistical significance. Laboratory tests revealed only minor changes in serum sodium, potassium, chloride, and uric acid in both groups throughout the treatment period, with the exception of chloride in the bumetanide group at 8 and 16 weeks. The patients who received extended treatment maintained a relatively stable state. No clinical adverse reactions were considered to be related to either drug. Both diuretics proved equally effective in reducing edema. The effective dose ratio of bumetanide:furosemide was 1:25.