INTRODUCTION: In critically ill patients with hematologic malignancies, acute kidney injury (AKI) usually occurs in the context of multiple organ failure due to various etiologies and is associated with poor prognosis. The objective of the present study was to identify the prognostic factors associated with intensive care unit (ICU) mortality in patients with hematologic malignancies and AKI requiring renal replacement therapy (RRT). METHODS: We retrospectively evaluated 94 patients with hematologic malignancies and AKI who received RRT in the ICU of Samsung Medical Center, Seoul, Korea, between January 2004 and December 2007. RESULTS: The study sample included 65 men and 29 women with a median age of 49 years (interquartile range [IQR], 36-61 years). The median Simplified Acute Physiology Score II and Sequential Organ Failure Assessment (SOFA) scores at ICU admission were 64 (IQR, 46-79) and 13 (IQR, 9-16), respectively. The RRT for AKI was initiated at a median time of 1 day (IQR, 0-4 day) after ICU admission. Seventy-two (77%) patients died in the ICU after a median time of 4 days (IQR, 2-20 days) after the initiation of RRT. Among the 22 patients who survived, 5 (23%) required RRT after ICU discharge. Intensive care unit mortality was associated with an etiology of AKI, Simplified Acute Physiology Score II score, and SOFA score. Modified SOFA (mSOFA) score (defined as the sum of the 5 nonrenal components of the SOFA score) at the initiation of RRT was lower in survivors than in nonsurvivors. In a multiple logistic regression analysis, ICU mortality was independently associated with mSOFA score (odds ratio, 1.83 per mSOFA score increase; 95% confidence interval, 1.38-2.42) at the initiation of RRT. The estimated area under the curve for mSOFA score was 0.902 (95% confidence interval, 0.831-0.972). CONCLUSION: The severity of organ failure, excluding renal failure, at initiation of RRT was independently associated with ICU mortality in patients with hematologic malignancies and AKI requiring RRT.