Objective: Although obesity is related with cardiovascular disease, the exact mechanism of the relationship is not fully understood. We aim to examine the relationship between plasma viscosity and obesity as a cardiovascular disease risk factor in obese and non-obese groups. Methods: We recruited 75 obese subjects (mean age: 40.2 +/- 8.4 years, Body Mass Index: 33.61 +/- 2.57 kg/m(2)) who were admitted to the Clinic of Endocrinology and Metabolism of Cerrahpasa Medical Faculty. As a non-obese group (n=70, mean age: 41.78 +/- 9.7 years, Body Mass Index: 21.84 +/- 3.42 kg/m(2)) healthy subjects from medical and laboratory staff were selected. Plasma viscosity and lipid profile were measured and atherogenic index was calculated as atherogenic risk factors. Results: Plasma viscosity, total cholesterol and LDL-cholesterol levels and atherogenic index were significantly increased in obese group compared to non-obese group for each p < 0.001. We found no significant difference in plasma fibrinogen, insulin, albumin and HDL-cholesterol levels between obese and non-obese groups. Plasma viscosity was correlated with total cholesterol and atherogenic index only in the obese group (p < 0.05 and p < 0.05 respectively). In the non-obese group regarding PV, we determined a positive correlation with triglycerides (r: 0.470, p < 0.05) and negative correlation with HDL-C (r: -0.518, p < 0.05). Conclusion: Plasma viscosity, an early atherosclerotic risk factor, might be helpful in the assessment of cardiovascular risk in obese subjects along with classical cardiovascular risk factors such as plasma cholesterol and atherogenic index.