Fifteen patients with chronic liver disease having a peritoneovenous shunt for chronic intractable ascites were studied prospectively for renal function and hemodynamic changes during balance studies, pre-, peri-, and postoperatively. Shunt insertion caused a rapid redistribution of ascites into the intravascular compartment with hemodilution and significant rises in cardiac output (9 patients) (P less than 0.025) renal blood flow (3 patients) (P less than 0.025), and creatinine clearance (15 patients) (P less than 0.005), and decreases in plasma renin activity (10 patients) and serum aldosterone levels (9 patients) (P less than 0.025). Despite these changes, small repeated doses of furosemide were required to start and maintain a diuresis and natriuresis with sodium excretion rising from 7.2 +/- 4.1 to 174 +/- 44 meq/day (P less than 0.0005) in the 15 patients. At 2 wk postoperatively, the 15 patients had lost a mean of 7.5 kg in weight associated with a persistent improvement in creatinine clearance and a continued natriuresis, 15.9 +/- 7 mEq/day (P less than 0.005), despite no statistically significant change in cardiac output (7 patients) or renal blood flow (4 patients) compared with preoperative levels. This operation is an effective therapy for refractive ascites, but the incidence of potentially fatal complications makes us hesitate to recommend it except for patients resistant to normal conservative measures.