The purpose of this study was to investigate the effect of dietary zinc levels on carbohydrate metabolism and serum zinc, magnesium and chromium contents in obese rats. Animals were divided into three groups by zinc levels, such as low (15 ppm), adequate (30 ppm) and high (60 ppm) levels of dietary zinc. The food intake, weight gain and feed efficiency ratio were not changed by zinc levels. There were no significant differences in liver, kidney and spleen weights. However, serum glucose concentration significantly decreased as the levels of dietary zinc increased, in particular, that of obese rats fed the high level of zinc was remarkably decreased. Insulin concentration of rats fed high level of zinc diet was significantly higher than that in the other groups. However, there were no significant differences in serum zinc and chromium contents, although serum magnesium fed zinc deficient diet was significantly higher than that of the other two groups. Glucose concentrations had negative correlation with insulin concentrations, and positive correlations with serum magnesium content. In conclusion, serum glucose concentrations were decreased and insulin concentrations were increased as the levels of dietary zinc increased in obese rats. These results suggested that zinc supplement at higher level than adequate one would increase insulin concentration and may improve hyperglycemia problem in obese groups.