To assess the contribution of a replacement of Trp at codon 64 of beta 3-adrenergic receptor by Arg to fat distribution and metabolic disturbances in Japanese general population, we examined the missense mutation in 1122 persons consisting of 817 men aged 50.0 +/- 8.9 years and 305 women aged 50.8 +/- 8.5 years in Kyushu, Japan. The incidence of Arg64 allele was 0.21; no age-dependent decrease of the allele frequency was observed, suggesting that the mutation was not associated with early mortality. The genotype was not significantly correlated with body mass index or the thickness of visceral fat estimated by ultrasonography. Glucose tolerance and glucose-induced insulin secretion were not significantly different among subjects with Trp/Trp, Trp/Arg and Arg/Arg at codon 64. Although in obese persons the ratio of heterozygotes for the mutation tended to be higher in subjects with impaired glucose tolerance than in subjects with normal glucose tolerance, the tendency was not observed in non-obese persons. Furthermore none of 39 non-obese individuals homozygous for the mutation was diabetic, whereas two out of six obese homozygous persons were diabetic. These observations suggest that the missense mutation may not be a main determinant of obesity in populations taking low fat/low energy Japanese-style diet and it may not be deleterious at least in non-obese individuals.