It has been suggested that athero-thrombotic risk progressively increases as the glomerular filtration rate (GFR) declines. Mean platelet volume (MPV) is the most commonly used measure of platelet size, and higher MPV value is independent risk factor for athero-thrombotic disease such as myocardial infarction. We aimed to evaluate the association between estimated GFR and MPV in patients with stable coronary artery disease showing normal to mildly impaired renal function. A total of 471 patients (288 males and 183 females; mean age: 62.5+9.5 years) with angiographically proven CAD were included. The patients were divided into two groups according to the estimated GFR value (GFRlow group: GFR <60 ml/minute per 1.73 m(2) and GFRhigh group: GFR ≥ 60, ml/min per 1.73 m(2)). Estimated GFR was calculated according to the Cockcroft-Gault formula. MPV, high-sensitive C-reactive protein (hsCRP) and other biochemical markers were measured in all patients. Prevalent of CAD was determined by the SYNTAX score. Patients with GFRlow group were of older age, had higher incidence of female gender, current smoker, diabetes, hypertension and hyperlipidemia, lower values of total cholesterol, LDL cholesterol, hemoglobin and platelet count and higher values of BMI, SYNTAX score, hs-CRP and MPV compared with patients with GFRhigh group. Multivariate linear regression analysis showed that the MPV was independently related with diabetes (β=0.189, p<0.001), eGFR (β=-0.267, p<0.001), hs-CRP level (β=0.158, p<0.001) and platelet count (β=-0.116, p=0.002). In conclusion, MPV is independently associated with GFR as well as hsCRP, platelet count and diabetes. These findings may explain, in part, the increase in athero-thrombotic risk with slightly impaired renal function.