Background: Continuous veno-venous hemodiafiltration (CVVHDF) is a preferred treatment modality in hemodynamically unstable acute kidney injury (AKI) patients, because it has advantages over intermittent dialysis in terms of hemo-dynamic stability. However, this patient group still shows a significantly high mortality rate. To aid in the management of these high-risk patients, we evaluated the risk factors for mortality in CVVHDF-treated hypotensive AKI patients. Methods: We studied 67 patients with AKI and hypotension who were treated with CVVHDF from February 2008 to August 2010. We reviewed patient characteristics and laboratory parameters to evaluate the risk factors for 90-day mortality. Results: Of the 67 enrolled patients (male:female¼42:25; mean age¼69714 years), 18 (27%) survived until 90 days after the initiation of CVVHDF. There was no significant difference in survival rates according to the etiology of AKI [hypovolemic shock 2/10 (20%), cardiogenic shock 4/20 (20%), septic shock 12/37 (32%)]. Univariate analysis did show significant differences between survivors and non-survivors in the frequency of ventilator use (44% vs. 76%, respectively; P¼0.02), APACHE II score (2977 vs. 3477, respectively; P¼0.01), SOFA score (1174 vs. 1374, respectively; P¼0.03), blood pH (7.370.1 vs. 7.270.1, respectively; P¼0.03), and rate of urine output o500mL for 12 hours (50% vs. 80%, respectively; P¼0.03). A multivariate Cox proportional hazards model showed that a urine outputo500mL for 12 hours was the only significant risk factor for 90-day mortality following CVVHDF treatment (odds ratio¼2.1, confidence interval¼1.01fi4.4, P¼0.048). Conclusion: A urine outputo500mL for 12 hours before the initiation of CVVHDF is an independent risk factor for 90-day mortality in hypotensive AKI patients treated with CVVHDF.