We have examined the hypothesis that the Gly972Arg variant of the insulin receptor substrate 1 (IRS1) gene is associated with the components contributing to overweight (obesity) and metabolic syndrome. We describe IRS1 genotype frequencies in 274 Korean men. The frequencies of Gly972Gly (GIG) and Gly972Arg (G/A variant) of the IRS1 gene were 88.3% and 11.7%, respectively, and the differences in frequencies between the overweight (BMI$geq$25kg/m$^2$) group and non-overweight (BMI<25kg/m$^2$) group were statistically significant. The subjects with G/A variant of IRS1 gene in non-overweight had significantly higher level of visceral fat thickness and adiponectin/leptin ratio than those with GIG alleles. In overweight group, the subjects with G/A variant of IRS1 gene also showed significantly higher level of insulin than those with GIG alleles. These results suggest that the IRS1 genetic polymorphism is involved in the occurrence of overweight, as well as metabolic syndrome.