Three hundred and seventy-seven children and adolescents aged 5-17 yr from the biracial (black-white) community of Bogalusa, Louisiana, were evaluated for Tanner stage of sexual development, plasma glucose, and insulin levels during an oral glucose tolerance test. Children of the two races were of similar age, weight, and height at each Tanner stage. Overall insulin response was compared by measuring the area under the insulin curve from the glucose tolerance test. Blacks, especially black females, had significantly higher insulin responses than their white counterparts. The insulin-glucose ratio at the initial t = 0 min baseline did not vary with race or sex throughout the Tanner stages. However, the 30 min postglucose data revealed clear differences between the races with blacks showing a higher insulin-glucose ratio. Ratios increased throughout puberty for both blacks and whites, boys and girls. The trends of racial contrasts seemed to be discernible even at the earliest stage of development. It is concluded that there is a clear difference between blacks and whites in insulin response to a glucose load early in childhood. These findings lead to the hypothesis that the greater prevalence of non-insulin-dependent diabetes mellitus seen in adult blacks, especially females, may be an expression of a difference in insulin secretion and related insulin resistance in early childhood.