Cholesterol and triglyceride lipid, lipoprotein as well as apolipoprotein A and B levels, are presented for Italian and Swiss schoolchildren of similar socio-economic origin, living in Geneva, and ranging in age from 8-9 and 14-15 years. This cross-sectional study revealed some differences associated with the ethnic origin of the participants. Furthermore subtle changes were related to age, associated with puberty and were sex-specific. Apolipoprotein A and B levels were found to be significantly related to age and less significantly to sex, whereas apolipoprotein A levels decrease with puberty, apolipoprotein B levels increase slightly. Of the 387 Italian and the 416 Swiss participants, 173 Italian and 193 Swiss children had a complete lipoprotein examination including apolipoprotein determination, whereas serum cholesterol and serum triglycerides were studied in the total group.