Serum lipid, lipoprotein cholesterol, and apolipoprotein (A-I and B) levels were compared between 940 black and 1710 white children who were between the ages of 5 and 17 years. Stratification, matching, and analysis of covariance were used to determine whether black-white differences in levels of serum triglycerides (TG), very low- (VLDL-C), and high- (HDL-C) density lipoprotein cholesterol, and apolipoprotein A-I (apoA-I) could be explained by differences in sexual maturation, obesity, cigarette smoking, alcohol intake, oral contraceptive use, insulin, and glucose. Independently of these covariates, blacks had elevated levels of HDL-C and apoA-I (males only), and whites had increased levels of TG and VLDL-C. All differences were statistically significant at the 0.001 level. In addition, racial contrasts tended to be greater in sexually mature, as compared with prepubertal, males; a similar divergence of levels with sexual maturation was not observed in females. HDL-C levels in white males were partially explained (R2 = 0.12) by sexual maturation, insulin, and obesity; apoA-I levels were associated with only sexual maturation and insulin. Racial differences in levels of serum lipids, lipoprotein cholesterol, and apoA-I in early life, therefore, exist independently of differences in several lipoprotein determinants. Since the initial stages of atherosclerosis begin in the young, these black-white lipoprotein contrasts may influence differences in adult coronary heart disease rates between the races.