Sixty eight children born in 1977 who were taking part in an unrelated study of childhood asthma were selected to have their serum cholesterol concentrations measured at birth, and at 4 months and 1, 2, 3, 4, 5, and 11 years of age. Concentrations of high density lipoprotein were measured at 5 and 11 years.Cholesterol values increased rapidly from birth and plateaued at 1 year. There was a further small rise just before puberty. Tracking of values was seen after the age of 1 year, but did not become established until 4 years of age. The cholesterol concentrations in girls were marginally higher than those in boys. The mean (SD) values of cholesterol (mmol/l) for boys were: at birth, 1.7 (0.4); at 1 year, 3.9 (0.9); at 5 years, 5.2 (1.9); and at 11 years, 5.0 (0-7). For girls the corresponding figures were: at birth, 1-9 (0.6); at 1 year, 4-7 (1-0); at 5 years, 4-6 (0.7); and at 11 years, 5-1 (0-7). The mean (SD) high density lipoprotein concentrations (mmol/l) for boys were: at 5, [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]