The aim of this study was to investigate crosssectionally the prevalence and covariates of obstructive sleep apnea syndrome (OSAS) and its relationship to metabolic syndrome (MS), insulin resistance (IR), and coronary heart disease (CHD) in a population sample of 1,946 men and women representative of Turkish adults. OSAS was identified when habitual snoring and episodes of apnea were combined with another relevant symptom. MS was diagnosed based on modified criteria of the Adult Treatment Panel III and IR by homeostatic model assessment (HOMA). OSAS was identified in 61 men (6.4%) and 58 women (5.8%), at a similar prevalence, after adjusting for covariates. Among individuals with OSAS, significantly higher odds ratios (ORs), adjusted for age, body mass index (BMI), and waist girth, were observed for MS, hypertension, and prevalent CHD, but not for HOMA or menopause. Significantly higher C-reactive protein existed only in women with OSAS who were also more frequent smokers. In logistic regression models, waist circumference, but not BMI nor hypertension, was significantly associated with OSAS among men. In women, by contrast, current cigarette smoking and hypertension were the significant independent covariates. Regression models controlling for sex, age, and smoking revealed that MS (and not IR per se) was associated significantly with OSAS (OR 1.94) in nondiabetic individuals. To conclude, abdominal rather than overall obesity in men and smoking among women are significant independent determinants of OSAS in Turkish adults. OSAS is associated with MS rather than IR per se. Relatively high prevalence of OSAS is observed in Turkish women in whom it is significantly associated with CHD.