Fourteen black and 16 white healthy adolescents underwent a 2-hour hyperglycemic clamp (12.5 mmol/L) to investigate racial differences in insulin secretion and sensitivity. First-phase and second-phase insulin concentrations were higher in black subjects than in white subjects (first phase: 944 ± 110 pmol/L vs. 462 ± 52 pmol/L, p= 0.0003; second phase: 1050 ± 146 pmol/L vs. 652 ± 53 pmol/L, p = 0.0012). The insulin sensitivity index was lower in black adolescents (8.21 ± 1.05) compared with white adolescents (12.55 ± 1.42 μmol/kg per minute per picomole per liter, p = 0.02). These findings indicate that significant differences in insulin secretion and sensitivity are detectable in healthy black versus white adolescents. (J PEDIATR 1996;129:440-3)