The present study was aimed to evaluate serum leptin level and the frequency of oligopolymorphic codon 25 (CAA/CAG) of Ob gene in Behcet's disease. Eighty-seven patients with Behcet's disease and 85 healthy controls with matched age, gender and body mass index were included in the study. Serum leptin level was determined and genotype of codon 25 of Ob gene was performed by using the PCR amplification after DNA extraction. Serum leptin concentration of the patients with Behcet's disease (23.8 ± 22.8 ng/ml) was higher than that of the control groups (17.1 ± 14.7 ng/ml). The patients with Behcet's disease and control subjects showed CAA/CAA genotype, indicating the presence of no polymorphism. Neither Behcet's disease nor serum leptin level was found to be related to codon 25 polymorphism. We concluded that leptin 25CAG polymorphism is not associated with Behcet's disease and serum leptin level. © Springer-Verlag 2006.