Diapamide is an effective diuretic and saluretic agent in rats, dogs, and monkeys. A pharmacologic animal study indicated that diapamide may be equal or superior to furosemide in experimentally induced congestive failure. Diapamide possessed the ability to induce water loss approximately equally from cells and extracellular fluid with or without the presence of excess water. The most frequently occurring ad- verse reaction was mild to moderate nausea, diarrhea and vomiting. In human, urine output with furosemide was significantly greater than with diapamide. Thus, diapamide would appear to serve a role between the milder thiazide diuretics and the more effective furosemide.