Objective. To investigate body fat composition, measured by bioelectrical impedance assay (BIA), for predicting the presence and severity of obstructive sleep apnea-hypopnea syndrome (OSAHS). Body fat composition was also compared with other well-known OSAHS predictors such as body mass index (BAR), neck circumference, and abdominal visceral fat. Study Design: A prospective study was designed. Fifty-one patients (41 male, 10 female), who were referred to Hacettepe University Faculty of Medicine, Department of Otorhinolaryngology, Head and Neck Surgery with suspected OSAHS, between April 2003 and June 2004, were included in the study. Methods: All patients underwent polysomnography (PSG) and were classified according to their apnea-hypopnea index (AHI) into four groups. The cross-sectional area of abdominal visceral fat was measured by computed tomography (CT) scanning in 33 of the patients. Neck circumference and BMI was measured for all patients. BIA was performed to determine body fat composition. The groups were compared, and correlation of the variables with AHI was investigated. Results: Of the variables, BMI and percentage of body fat (determined by BIA) were found to be significantly correlated with AHI (r = 0.782, r = 0.647). CT of cross-sectional area of abdominal visceral fat provided 100% sensitivity and specificity (P < .001) in differentiating simple snorers from OSAHS patients. By combining percentage of body fat and body fat mass, higher levels of sensitivity (95%) and specificity (100%) were achieved for diagnosis of OSAHS. Conclusion: It was concluded that the BIA could be an inexpensive and practical alternative to prePSG screening tests and should be included in the evaluation of OSAHS patients.