Sir: Since apolipoproteins (Apo) are known to be reliable biological indices of atherogenic risk [1, 2], a transversal study was per formed to determine the values of A p o A and B in 159 hospitalised children aged 1 mon th -14 years without gastroenteric disorders or o ther diseases that could significantly modify the apoprotein profile. Values were compared with the respective H D L and LDL-fract ions of cholesterol and with sex (Table 1). Total and fract ionated blood protein values were normal in all cases as were the other commonly assayed parameters for growth evaluation. A p o A and B values were assayed (simple immuno-diffusion in agar-gel) after 8 h fasting together with H D L C and LDL-C. Group 1 included infants aged 1-12 months because mean values were the same for the younger (1-6 months) as the older (6-12 months) infants. Mean A p o A values decrease in the 2nd year of life (more markedly in girls) and are slightly higher at puberty than in the 1st year. H D L C values follow the same trend. In girls aged 12-24 months mean A p o A and H D L C values are lower than in boys.