Introduction: In Behçet's disease (BD), during recurrent inflammatory attacks, various vasculitic involvements may be seen in different systems. It is difficult to measure disease activity in these patients, because disease presents with attacks and relapses and there is no specific laboratory test that encompasses all findings of disease. The aim of the present study was to investigate the relation between clinical activity of BD disease and mean platelet volume (MPV). Methods: 200 patients meeting 1990 classification criteria of International Behçet's disease Study Group and who were followed between October 2011 and June 2012 in Multidisciplinary BD outpatient clinic were included in the study. Files of BD patients in the archive of BD outpatient clinic and data recorded in Electronic Health Records were examined. Results: Patients were divided into two groups, patients with or without active disease were named group 1 and group 2, respectively. In all BD patients, independently from disease activity, no significant difference was found between the patients with a history of thrombosis and those without it with respect to MPV (9.12 vs 8.89 fl, respectively, p=0,117). In patients with active disease, MPV values were significantly higher than those without active disease (9.43 vs 8.41 fl, respectively, p<0.05). Among patients with active disease (group 1), no significant difference was found in MPV values of those with a history of thrombosis and those without it (9.47 vs 9.27 fl, p>0.05). Conclusion: The higher MPV values in BD patients seem to be independent factor predicting disease activity.