We investigated the association between a brain-derived neurotrophic factor (BDNF) gene polymorphism and clinical features in a sample of patients with obsessive-compulsive disorder (OCD). A total of 100 patients diagnosed with OCD according to the Diagnostic and Statistical Manual IV criteria and 110 control subjects were included in this study. The distribution of a single nucleotide polymorphism rs2883187 was compared in OCD patients and normal controls. Clinical features were compared between the subgroups of OCD patients with different genotypes. There was no significant difference for the allele frequencies and genotype distributions between the OCD and control groups. The Hamilton Anxiety Rating Scale, Yale-Brown Obsessive Compulsive Scale obsession and total scores were found to be higher in patients with the CC genotype than in the patients who are homozygous for the T allele. The rates of OCD in first-degree relatives of OCD patients who were homozygous for the C allele were significantly higher,. compared to those with CT and TT genotypes. Our results indicate that the CC genotype may be associated with the severity and increased familial loading of OCD. Further investigation based on larger populations is needed to reveal the full association of the BDNF polymorphism with OCD. (C) 2013 Elsevier Ltd. All rights reserved.