BACKGROUND: The aim of this study was to exam the clinical features and the renal outcome of HELLP syndrome complicated with ARF. METHODS: Thirty-nine patients with HELLP syndrome were retrospectively analyzed on the basis of medical records. A serum creatinine level of >1.3 mg/dL was used as a criterion to define ARF for at least 48 hours. RESULTS: Of the 39 patients, HELLP syndrome with ARF developed in 17 patients. The ARF group had a higher incidence of primigravida (p<0.05) and a longer gestational age at the onset of HELLP syndrome (p<0.05) than those in the non-ARF group. The recovery time of HELLP syndrome in the ARF group was much longer than that in the non-ARF group (p<0.05). In the ARF group, the serum aspartate aminotransferase (AST) concentration was higher (p<0.05) and the nadir blood platelet counts were lower (p<0.05). The incidence of disseminated intravascular coagulation (DIC) was significantly higher in the ARF group than in the non-ARF group (p<0.01). There was no significant difference in the incidence of pulmonary edema, abruptio placenta, preeclampsia, and fetal death between the two groups. Only one patient in the ARF group required hemodialysis. In all ARF patients, the renal impairment fully recovered within a median of 5 days (range: 2-32 days) after the onset of ARF. CONCLUSION: The clinical factors associated with ARF in HELLP syndrome were primigravida, gestational age, serum AST level, blood platelet counts, and DIC. The ARF in HELLP syndrome fully recovered without progression to permanent renal impairment.