In the bone marrow transplant setting, several authors hypothesized that severely overweight patients are at increased risk of transplant-related toxicity, but different definitions of obesity, different body weight groupings and heterogeneous samples of patients were analyzed. To overcome these limitations, we retrospectively considered a homogeneous group of 54 patients (median age 36.5 years), with a diagnosis of de novo acute myeloid leukemia (AML), autografted in first complete remission (CR) with the Bu-Cy2 conditioning regimen, dosed on actual body weight. Patients were classified into three groups (obese, non-obese, underweight) using body mass index (BMI = kg/m(2)); for each group we analyzed transplant-related toxicity and mortality, overall survival and disease-free survival (OS/DFS). In spite of the relatively small number of patients, in our results high BMI appears a predictive factor for an increase of treatment-related toxicity and mortality. Moreover, 30 (55%) patients are currently alive in continuous CR, and after a median follow-up of 76.5 months (range 14-137) statistically significant differences in OS and DFS were detected between obese and non-obese groups (P = 0.012 and 0.021, respectively). Our study suggests that obesity may represent an independent risk factor for autograft in AML and further investigations are warranted.