Previous studies of body fat using tape measurement of body circumference and hand-held caliper skinfold measurements have suggested abnormal fat distribution in patients with diabetes mellitus. These methods, however, have high interobserver variability and cannot assess intra-abdominal fat independent of subcutaneous fat. We used computed tomography to evaluate body fat distribution in a group of 53 Japanese-American men of similar age and body mass index (weight divided by height squared). As determined by a 75-g oral glucose tolerance test, 29 subjects had type II diabetes and 24 were normal. Computed tomography cuts were obtained at three body levels to measure thorax, abdomen, and thigh subcutaneous fat area as well as intra-abdominal fat area. We found greater intra-abdominal fat in men with diabetes than in those without (123.74 vs. 95.54 cm2, P = 0.034) and a greater ratio of thorax to thigh subcutaneous fat (2.55 vs. 1.88, P = 0.016). These findings support the hypothesis that fat in different areas of the body differs metabolically. Computed tomography can be a useful tool for investigating whether abnormal body fat distribution is associated with the pathogenesis of abnormal glucose tolerance.