The aim of the present study was to evaluate the relationship between oligopolymorphism in the 25th codon of leptin gene and obesity. Eighty-seven obese women and 75 healthy women were constituted obese and control groups. Body fat percent, fat mass and lean body mass were determined by bioimpedance meter and leptin levels were determined. The presence of 25th codon oligopolymorphism in the leptin gene was done by PCR-RFLP technique. Mean leptin levels were 38.5±22.0ng/ml, and 147.9±44.8ng/ml in the control and obese groups, respectively. The correlations of serum leptin level to body fat percentage and fat mass in the control group were significant. The correlations in the obese group were not significant. This data implies that the difference of leptin levels between control and obese groups are more likely to be associated with alterations in the leptin gene other than 25th codon or alterations in the leptin receptor gene.