Obesity has been previously suggested as an adverse prognostic marker in patients with acute leukemia. To evaluate the relationship between obesity and clinical outcome, disease-free survival (DFS) and overall survival (OS), in patients with acute myelogenous leukemia (AML), including acute promyelocytic leukemia (APL), we performed a pooled analysis of four CALGB (Alliance) clinical trials. Our study included 446 patients with APL from CALGB 9710, and 1,648 patients between 18 and 60 years of age with non-APL AML from CALGB 9621, 10503, and 19808. Obesity was defined as BMI ≥30 kg/m(2). Multivariate Cox proportional-hazard regression models were fitted for DFS and OS. Obesity was seen in 50% and 38% of APL and non-APL AML patients, respectively. In APL patients, obesity was associated with worse DFS (HR 1.53, 95% CI 1.03-2.27; P = 0.04) and OS (HR 1.72, 95% CI 1.15-2.58; P = 0.01) after adjusting for age, sex, performance status, race, ethnicity, treatment arm and baseline white blood cell count. Obesity was not significantly associated with DFS or OS in the non-APL AML patients. In conclusion, our study indicates that obesity has significant prognostic value for DFS and OS in APL patients, but not for non-APL AML patients.