In the process of lipolysis, adipocytes are stimulated by catecholamines through β1, β2, and β3 adrenergic receptors (ARs). So far, β2 and β3 AR polymorphisms have been reported related to obesity. However, the relation of β1AR polymorphisms to obesity has not been evaluated. In the present study, we examined whether βAR polymorphisms are associated with obesity-related phenotype in type II diabetic patients. Polymorphisms of β1Ser49Gly, β1Arg389Gly, β2Arg16Gly, β2Gln27Glu and β3Trp64Arg were genotyped in 188 type II diabetic patients by PCR-RFLP. Among these polymorphisms, β1Ser49Gly was found to be associated with obesity. Subjects with β1Gly49 allele showed higher body mass index (BMI) than those with Ser49/Ser49 genotype (24.7±3.7 vs. 23.4±3.3 kg/m2; p=0.031). Subjects with β1Gly49 allele were more frequently overweight (BMI≥25 kg/m2) compared with β1Ser49 homozygous group (42.1 vs. 24.4%, p=0.015). By multiple linear regression analysis, β1Ser49Gly polymorphism was independently associated with higher BMI (p=0.019, β=0.166). Our data indicate that the Gly49 allele in β1AR is associated with higher BMI in type II diabetic patients. Genotyping for β1Ser49Gly polymorphism in type II diabetic patients may have clinical benefit to predict obesity, thereby contributing to the prevention of insulin resistance.