The procoagulant and prothrombotic states in patients with chronic atrial fibrillation are higher than those in patients with normal sinus rhythm. Mean platelet volume (MPV) which is a marker of platelet function and activation can reflect changes either in the level of platelet stimulation or the rate of platelet production. In this study, we aimed to assess and compare the hematologic parameters of routine complete blood count analysis in elderly patients with nonvalvular atrial fibrillation and control individuals with normal sinus rhythm. One hundred and seven consecutive patients with nonvalvular chronic atrial fibrillation and 112 age and sex-matched control individuals with normal sinus rhythm were retrospectively included in the study from the outpatient cardiology clinic. Hematological variables, including MPV, platelet count, red blood cell and white blood cell count were measured in all patients and control individuals. Presence of coronary artery disease, hypertension, sex, hyperlipidemia, diabetes mellitus, smoking status, hematocrit and platelet count were comparable between two groups (P>0.05 for all). However, MPV and white blood cell count were significantly higher in patients with atrial fibrillation compared to those without atrial fibrillation. Logistic regression analysis revealed that white blood cell count and MPV significantly and independently associated with atrial fibrillation. We have shown that MPV and white blood cell count is independently associated with chronic nonvalvular atrial fibrillation. To improve the clinical utility of MPV and role of inflammation in the pathogenesis of atrial fibrillation, further studies are needed to be carried out. (C) 2013 Wolters Kluwer Health vertical bar Lippincott Williams & Wilkins.