Peroxisome proliferator-activated receptors (PPARs) are a nuclear hormone receptor superfamily of ligand-activated transcription factors, and the PPARgamma subtype regulates adipocyte differentiation, lipid metabolism, and insulin sensitivity. There have been several reports on the relationship between the PPARgamma2 Pro12Ala genotype and obesity or diabetes in Caucasians. The objective of this study was to examine the relationship between this mutation and obesity or diabetes in Korean subjects. Two hundred and twenty-nine Korean subjects, including 111 obese subjects (body mass index, >25 kg/m2) were included in this study. One hundred and eleven subjects had normal glucose tolerance, 60 had impaired glucose tolerance, and 58 had diabetes mellitus. We evaluated these subjects for the Pro12Ala mutation in the PPARgamma gene using PCR-restriction fragment length polymorphism. Allele frequencies of the Pro12Ala missense mutation of PPARgamma2 were not different among Korean subjects with normal glucose tolerance (qAla = 0.045), those with impaired glucose tolerance (qAla = 0.033), and those with diabetes mellitus (qAla = 0.043; P > 0.05). Allele frequencies of PPARgamma2 Ala in obese subjects (qAla = 0.036) were not significantly different from those in nonobese subjects (qAla = 0.047). These results suggest that the Pro12Ala mutation in PPARgamma is not associated with either diabetes or obesity and may not be an important determinant of obesity or diabetes in Korean subjects.