The Ala12 allele of the peroxisome proliferator-activated receptor gamma gene (PPARG2) has been associated with reduced risk of type 2 diabetes mellitus (T2DM) and increased whole-body and skeletal muscle insulin sensitivity in nondiabetic subjects. The effect of the Pro12Ala polymorphism on tissue specific insulin sensitivity in subjects with T2DM has not been previously investigated. We studied the effect of the Pro12Ala polymorphism on the rates of whole-body, skeletal muscle, and subcutaneous adipose tissue glucose uptake (GU) in T2DM subjects, and the rates of hepatic GU in nondiabetic and T2DM subjects during hyperinsulinemia. Our study included 105 T2DM subjects whose whole-body, skeletal muscle, subcutaneous adipose tissue, and hepatic GUs were measured using (18)F-fluorodeoxyglucose and positron emission tomography during the hyperinsulinemic euglycemic clamp. Hepatic GU was also measured in 68 nondiabetic subjects. In obese (body mass index >or=27 kg/m(2)) subjects with T2DM, the rate of hepatic GU was 28% lower in subjects with the Pro12Pro genotype than in carriers of the Ala12 allele (P = .001); and a similar trend was observed in nondiabetic obese subjects (P = .137). No effect of the Pro12Ala polymorphism on the rates of whole-body, skeletal muscle, or subcutaneous adipose tissue GU was observed in T2DM subjects. We conclude that the Ala12 allele of PPARG2 is associated with higher hepatic GU in obese subjects with T2DM.