It has recently been shown that repeated large-volume paracentesis associated with intravenous albumin infusion is a rapid, effective, and safe therapy of ascites in cirrhosis. To investigate whether intravenous albumin infusion is necessary in the treatment of cirrhotics with large-volume paracentesis, 105 patients with tense ascites were randomly allocated into two groups. Fifty-two patients (group 1) were treated with paracentesis (4-6 L/day until disappearance of ascites) plus intravenous albumin infusion (40 g after each tap), and 53 (group 2) with paracentesis without albumin infusion. After disappearance of ascites, patients were discharged from the hospital with diuretics. Patients developing tense ascites during follow-up were treated according to their initial schedule. Paracentesis was effective in eliminating the ascites in 50 patients from group 1 and in 48 from group 2, with the duration of the hospital stay being approximately 11 days in both groups. Paracentesis plus intravenous albumin did not induce significant changes in standard renal function tests, plasma renin activity, and plasma aldosterone. In contrast, paracentesis without albumin was associated with a significant increase in blood urea nitrogen, a marked elevation in plasma renin activity and plasma aldosterone concentration, and a significant reduction in serum sodium concentration. One patient from group 1 and 11 from group 2 developed renal impairment or severe hyponatremia after treatment, or both (chi 2 = 9.19; p less than 0.01). The development of these complications could not be predicted by clinical and laboratory data before treatment. Although the probability of survival after entry into the study was similar in patients from both groups, a multivariate analysis identified the development of hyponatremia or renal impairment, or both, following the first paracentesis treatment and the occurrence of other complications during the first hospitalization (encephalopathy, gastrointestinal bleeding, and severe infection) as being the only independent predictors of mortality. These results indicate that intravenous albumin infusion is important in avoiding renal and electrolyte complications and activation of endogenous vasoactive systems in cirrhotics with ascites who are treated with repeated large-volume paracentesis. The development of such complications may impair survival in these patients.