OBJECTIVE To examine sibling aggregation of low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), apolipoprotein (apo) B and apo A-I in white versus black school-aged children. METHODS Study subjects included 790 full sibships representing 1305 sibpairs aged 5 to 17 years from a biracial community. METHODS Intraclass correlation coefficients estimated by analyses of covariance were used to examine sibling aggregation of LDL-C, HDL-C, apo B and apo A-I. The influences of obesity and other lifestyle variables on sibpair differences in LDL-C, HDL-C, apo B and apo A-I were evaluated in black and white children by stepwise multiple regression analyses. RESULTS Intraclass correlation coefficients for LDL-C and apo B in black children were lower than those in white children (0.17 and 0.11 versus 0.32 and 0.33, respectively, P < 0.05-0.01); no racial difference was found for HDL-C and apo A-I. Intraclass correlation coefficients for LDL-C and HDL-C were similar to that of apo B and apo A-I, respectively and the sibpair differences in LDL-C and HDL-C were correlated with those of apo B and apo A-I, respectively (P < 0.01). Obesity exerted a greater effect on sibpair differences in LDL-C, HDL-C and apo B in black children than in white children. CONCLUSIONS These results suggest that the hereditary influence on LDL-C and apo B is more important in white children than in black children, especially for apo B. Further, genetic influence on LDL-C versus apo B, or HDL-C versus apo A-I may be similar.