Glucose transporter genes have been proposed as candidate genes for type 2 (non-insulin-dependent) diabetes mellitus. We chose to study the adult skeletal muscle glucose transporter gene (GLUT 4) andGLUT 1 in consideration of previous conflicting results obtained by different authors. We studied 68 patients with type 2 diabetes, and 66 non-diabetic controls matched for age, sex, and body mass index (BMI). Women and men were considered separately, according to BMI (≤24.0 and >24.0 for women; ≤25.0 and >25.0 for men). Allele and genotype frequencies were not significantly different in controls and in type 2 diabetic patients. ForGLUT 1 allele 1 and genotype x1x1 were more frequent, although not significantly (P=0.064 at χ2,P=0.025 at Fisher exact test) in overweight/obese diabetic women than in overweight/obese non-diabetic women. These data do not support the hypothesis that these genes play a major role in genetic susceptibility to type 2 diabetes mellitus, but suggest a possible association, at least in women, of allele 1 ofGLUT 1 with obese type 2 diabetes mellitus.