The purpose of this study was to investigate plasma adiponectin concentration and its relation with metabolic parameters in overweight and normal weight subjects. The study was carried out in 46 overweight subjects (20 male, 26 female; mean age 39.4 +/- 10.2 years) and 48 (19 male, 29 female; mean age 36.1 +/- 10.6 years) sex- and age-matched normal weight subjects. Anthropometric measurements were recorded and adiponectin, glucose, insulin, lipid profile, total homocysteine (tHcy) and fibrinogen levels were measured. The insulin resistance index was assessed by homeostasis model assessment for insulin resistance (HOMA-IR). Plasma mean adiponectin concentrations of the overweight subjects were significantly lower than those of normal weight subjects (15.0 +/- 4.2 vs 17.3 +/- 5.6 ng/ml) (P < 0.05). In overweight subjects, adiponectin levels negatively correlated with body weight (r = -0.35, P < 0.001), body mass index (BMI) (r = -0.28, P < 0.006), systolic blood pressure (r = -0.21, P < 0.04), fasting insulin (r=-0.19, P < 0.01) and HOMA-IR (r=-0.20, P < 0.01) and positively with high-density lipoprotein cholesterol (HDL-C) (r = 0.27, P < 0.009). Overweight subjects with low HDL-C levels had significantly decreased plasma adiponectin levels compared to those with high HDL-C levels (P < 0.05). Multiple regression analysis revealed that BMI, HOMA-IR and HDL-C explained 12%, 20% and 15% variance of the adiponectin concentrations. These findings may suggest that circulating adiponectin is associated with insulin resistance and HDL-C levels independent from BMI in overweight subjects.