HELLP syndrome, a syndrome of hemolysis, elevated liver enzymes and low platelets may occur in pregnancy with pre-eclampsia/eclampsia, and its a significant complication is acute renal failure (ARF). The aim of study was to determine frequency and outcome of HELLP syndrome complicated by ARF. Thirty-nine patients with pregnancy-related ARF were treated between Jan 1, 1989 and Jan 1, 1999. In these patients, the most frequent causes were HELLP syndrome (n = 14; 36%), postpartum hemorrhage (n = 10; 26%), pre-eclampsia/eclampsia (n = 6; 15%) and abruptio placenta (n = 4; 10%). Seven of the patients with HELLP syndrome had impairment of consciousness during hospitalization. Of these patients, coma in 5, stupor in 1, confusion in 1 were diagnosed. Twelve of the patients with HELLP syndrome and 14 of the other patients were treated by dialysis. Mann-Whitney U test and chi2 test(corrected by Yates and Fisher exact) were used for statistical analysis. Although serious clinical findings, with supportive treatment, 12 patients with HELLP syndrome and 21 other patients were fully recovered. One patient both with and without HELLP syndrome could not recovered due to diffuse cortical necrosis. Moreover, one patient with HELLP syndrome and 3 other patients were died. Mortality rate of the patients with HELLP syndrome was not found different from those of the other patients (p = 0.544). The causes of death were cerebral hemorrhage in patient with HELLP syndrome and disseminated intravascular coagulation (n = 1), cerebral emboli (n = 1), adult respiratory distress syndrome (n = 1). Fetal death occurred in 4 patients with HELLP syndrome (28.5%) and 7 other patients (28%), and rates were similar (p > 0.5). Finally, HELLP syndrome was the most frequent cause leading to ARF in pregnancy and their prognosis was not different from those of the other patients.