1 The pharmacokinetics of frusemide have been studied in thirteen patients with severe chronic renal failure by using 35 S-frusemide. 2 The abosrption of aqueous frusemide was 57 +/- 20 percent (SD) and the bioavailability of 500 mg tablets was 42 +/- 12 percent, this differnece not assuming significance. 3 The renal clearance of frusemide was negligible (1.45 +/- 1.7 ml/min).