The effects of daily administration of 250-2,000 mg furosemide (F) were studied in patients on hemodialysis who still had residual renal function. In a short study, 10 patients (endogenous creatinine clearance 0.6-5.3 ml/min/1.73 m2) used 1,000 mg F twice daily during 7 days, and in a long-term study 13 patients (endogenous creatinine clearance 0.7-6.8 ml/min/1.73 m2) were treated during 1 year with 250-1,000 mg F orally each day. In the short study, we observed an increase in the 24-hour volume excretion with a median of 109% (p < 0.005). Urinary sodium excretion increased 210%, chloride 346% and potassium 65% when compared with the control period. In the long-term study, a marked initial rise in diuresis and electrolyte excretion was found. However, during a 1-year follow-up, a gradual decrease in response with time was found caused by progression of renal disease. There were no signs of ototoxicity. Side effects were bollous dermatosis on the limbs after exposure to sunlight during the summer (3 patients). We conclude that high-dose F is effective in patients on hemodialysis with residual urinary production. However, in the long term, the diuretic effects diminish because of progression of the underlying renal disease.