The peroxisome proliferator-activated receptor gamma 2 (PPARgamma2) has been studied extensively because of its putative role in adipocyte differentiation and insulin sensitivity. The association of the Pro12Ala and Pro115Gln PPARgamma2 gene variants with type 2 diabetes mellitus, the body mass index (BMI), and other diabetes-related phenotypes was examined in the Taiwanese population. Genotypes were determined by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) analysis. Allele frequencies were compared between 280 subjects with type 2 diabetes mellitus and 310 subjects without diabetes using the chi-square test. Continuous phenotype analysis was performed by multiple logistic regression adjusting for age and BMI where appropriate. There was no significant association between the Pro12Ala gene variant and type 2 diabetes; the frequency of the Ala12 allele was 0.03 in type 2 diabetics and 0.04 in nondiabetics (P = .40). The Gln115 allele was not detected in any of the cases or controls. In multiple linear regression analysis of all cases and controls combined adjusted for age, sex, and diabetic status, carriers of the Ala12 allele had a mean BMI of 25.9+/-0.5 kg/m2 (mean +/- SE), compared with 24.2+/-0.1 kg/m2 in Pro12 homozygotes (P < .001). In addition, carriers of the Ala12 allele have a 2.9 times (95% confidence interval [CI], 1.5 to 5.5) higher odds of having a BMI of at least 25 kg/m2. These results suggest that in the Taiwanese, the Pro12Ala PPARgamma2 gene variant may contribute to fat accumulation and a higher BMI independent of type 2 diabetes. These results need to be confirmed in future studies, as a linkage disequilibrium of this variant with other mutations cannot be ruled out.