Four consecutive patients with alcoholic cirrhosis and hepatorenal syndrome were treated with misoprostol, a synthetic methylester prostaglandin E1 analogue at twice the dosage advocated for anti-ulcer therapy (i.e., 0.4 mg four times per day orally) and albumin infusions. The mean urinary output obtained over the 3 days preceding misoprostol administration was 250, 315, 550 and 195 ml per 24 h, respectively, in the four patients, despite adequate volume expansion by plasma albumin to reach normal or high central venous pressure. Diuresis increased to 1450, 2440, 925 and 1300 ml, respectively, on days 2-4 after onset of therapy. Serum creatinine levels were 71, 51, 33 and 35 mg/l before and dropped to 26, 21, 13 and 17 mg/l during treatment. All patients had hyponatraemia (117-128 mequiv/l) which normalized, although they were continued on a low sodium intake of less than 10 mequiv per 24 h. Urinary sodium excretion increased from 0.4-3 mmol per 24 h, to 15-40 in the first two cases and only slightly to 3-5 in the last two patients. Three patients died after 10, 30 and 40 days due to oesophageal bleeding, encephalopathy or pulmonary infection, whereas one patient underwent an orthotopic liver transplantation when her serum creatinine attained a level of 13 mg/l. In the first patient, hepatorenal syndrome recurred 10 days after stopping the misoprostol treatment. High doses of misoprostol in the presence of adequate volume expansion thus seem to produce marked diuresis and creatininuria as well as mild natriuresis.(ABSTRACT TRUNCATED AT 250 WORDS)