Two patients with severe hepatorenal syndrome associated with alcoholic hepatitis are reported, in whom repeated daily courses of head-out water immersion were dramatically effective in producing an improvement of the renal function. Using repeated 2-hour courses of head-out water immersion for 7 days in the 1st patient, an immediate increase in urine output was observed. A slight increase in renal sodium excretion was also noted. The patient lost 7 kg over 1 week. Serum creatinine decreased from 520 to 370 mumol/l, and the renal function continued to improve thereafter. In the 2nd patient, repeated head-out water immersion was associated with a progressive improvement of the renal function, an effect that was absent during an initial therapy of volume load. The acute effects of immersion in in this 2nd patient were characterized by a dramatic increase in urine output and renal sodium excretion as well as in p-aminohippurate and creatinine clearances. These effects were associated with a decrease in the activity of the renin-angiotensin system and a modest increase in plasma atrial natriuretic peptide levels. Thus, these 2 cases emphasize the potential benefits of repeated head-out water immersions in improving the renal function of patients with hepatorenal syndrome.