The purpose of this study is to assess the relative effects of body fat distribution and obesity "per se" on serum glucose, insulin, and insulin resistance. Seventeen obese and nine nonobese control prepubertal girls were studied. Biceps, triceps, subscapular, and suprailiac skinfold thickness were measured. Percentage of body fat (% BF) and total body fat (TBF) were calculated. Body fat distribution was assessed by analyzing the central (suprailiac, subscapular)/peripheral (biceps, triceps) ratios. Oral glucose tolerance test was performed. Serum glucose and insulin were measured and insulinogenic index (insulin/glucose) was calculated. Body fat anthropometric data and body fat distribution indexes were significantly higher (p less than 0.001) in the obese group. The obese population presented significantly elevated values of glucose, insulin, and insulinogenic indexes (p less than 0.01-p less than 0.001). In the obese group, insulin showed significant positive correlations (p less than 0.05-p less than 0.001) with biceps, subscapular, and suprailiac skinfolds, % BF and TBF, whereas the insulinogenic index had positive correlations with suprailiac skinfold and TBF (p less than 0.05). Obese girls showed positive correlations between the body fat distribution indexes and insulin or insulinogenic indexes (p less than 0.05-p less than 0.001). In prepubertal girls obesity is of the centripetal (central) type. This pattern has an important role in determining the alterations in the glucose-insulin homeostasis that characterize the childhood nutritional obesity.