Objective: The aim of this study is to investigate the association between brain-derived neurotrophic factor (BDNF) Val66Met, Val66Val gene polymorphism and the characteristics of bipolar disorder (BD), obsessive compulsive symptoms within patients of BD. Methods: One hundred and six patients, diagnosed with BD according to the DSM-IV-TR criteria, were included in the study. All participants completed a sociodemographic questionnaire and they went through Structured Clinical Interview for DSM-IV Axis Disorders (SCID-I), Maudsley Obsessional Compulsive Questionnaire, Beck Depression Inventory and Beck Anxiety Inventory. DNA isolation was made from patients venous blood samples and on these DNAs BDNF gene polymorphism investigated by PCR-RFLP method. Results: Our results showed that 78 patients had BDNF Val66Val while 28 patients had Val66Met polymorphism. It was found that the patient group with Val66Val had an earlier age of onset of BD; moreover, in the Val66Met group, antidepressant induced mania episodes were significantly more frequent. No statistically significant difference was found between the two polymorphism groups with respect to obsessive compulsive symptoms. Discussion: It has been thought that some characteristics of BD maybe related with the BDNF gene val66val/met polymorphism. Our research partially supports this notion and more studies with larger samples are needed. [Anadolu Psikiyatri Derg 2013; 14(1.000): 10-18]