Objective: High body mass index (BMI) is associated with mortality in the general population, whereas obesity is suggested to confer a survival advantage in hemodialysis (HD) patients. However, underlying mechanisms are yet to be elucidated. We examined the cross-sectional association of BMI with inflammatory and nutritional markers and atherosclerosis in HD patients. Design: Cross-sectional study. Setting and participants: One hundred and nine maintenance HD patients in the Hacettepe University Hospital Haemodialysis Unit were studied. Methods: Data on demographics, comorbidity, and anthropometry were obtained by patient interviews. Atherosclerosis was assessed by B-mode Doppler ultrasonography on common carotid artery. Serum markers of inflammation, nutrition, and lipid metabolism, including C-reactive protein (CRP), albumin, prealbumin, homocysteine and lipoproteins, were measured by standard methods. Main outcome measure: Distribution of inflammatory and nutritional markers and prevalence of atherosclerosis in underweight, normal, overweight, and obese HD patients. Results: CRP levels were significantly higher in obese and underweight HD patients compared with normal and overweight patients (P < .05). The prevalence of atherosclerosis was significantly higher in underweight and obese patients (54.5% and 50%) compared with normal and overweight patients (25.7% and 33%) (P < .05). Conclusions: In the present study, obesity is associated with inflammation and atherosclerosis. An obesity-related survival advantage should be modified by other factors such as race, comorbid conditions, body composition, and nutritional status. (c) 2005 by the National Kidney Foundation, Inc.