Introduction: Tumor necrosis factor-α (TNF-α) is expressed primarily in adiposities, and elevated levels of this cytokine have been linked to obesity and insulin resistance. We, therefore, examined the relationship between this variant and obesity in an Iranian population. Materials and Methods: Subjects of the Tehran lipid and Glucose Study were classified in two age groups, the under 18 and the above 18 adults were classified in three groups according to their body mass index BMI<25, 25≤BMI<30, BMI≥30 subjects aged under 18 years were classified in the two groups according to their body mass index: under the 85th percentile for their age and sex and above the 85th percentile for their age and sex. Overall 239 persons were selected. We measured FBS, HDL-C, LDL-C, triglycerides, cholesterol levels and blood pressure, CRP, IL-6, IL-10, Adiponectin, and HOMA for all individuals. A 152 base pair segment of the mentioned gene with PCR was amplified and the polymorphism with RFLP (MSPI) revealed. Results: The allele frequency of TNF-α polymorphism was in the Hardy Weinberg equilibrium and the allele frequency was GG (79.5%), GA (19.2%), AA (1.3%) and there was no relation between BMI and the frequency of this allele. The genotype frequency in adolescents was GG (80.5%), GA (19.5%), AA(0%) 33 persons were GG genotype 8 GA genotypes and none had AA genotype. In adults, the genotype frequency was GG (79.3%), GA (19.2%), AA(1.5%) 157 persons had the GG genotype, 38 persons the GA genotype and 3 persons the AA genotype. Conclusion: No association was found between G-238A TNF-a promoter polymorphism and obesity, indicating probably that it is not an important risk factor for obesity or consequently for cardiovascular disease.