We studied in 2,153 children of both sexes from birth until 18 years of age, in Fuenlabrada, Madrid, the following parameters: the height, weight, tricipital and subscapular skinfolds, blood pressure, lipids, lipoproteins, glycemia, uric acid and smoking habits. We obtained the next mean values: Total cholesterol (TC), 166 +/- 36 mg/dl; triglycerides, 63 +/- 39 mg/dl; HDL-C, 53 +/- 13 mg/dl; LDL-C, 102 +/- 34 mg/dl; VLDL-C, 13 +/- 6 mg/dl. TC, HDL-C and LDL-C levels did not present any significant differences with respect to sex until 12 years of age. But they were significantly higher in girls than in boys in adolescence. In contrast, TG and VLDL-C levels were higher in girls than in boys until 12 years of age, they did not present any difference in adolescence. The significant change of the lipoproteinic pattern in adolescence is connected with the hormonal distribution that is produced in puberty.