The physigues of eighty pupils in a primary school in Shanyang were investigated after taking additional L-lysine hydrochloride with meals between classes for 12 weeks. They were derided into 3 groups: 1) ordinary diet plus 0.5g lysine; 2) ordinary diet plus 0.5g lysine and 5 mg iron (lysine and lysine-iron group were referred to as fortified group) and 3) ordinary diet only as control. After 12 weeks of experiment the results showed that the average increase in height, weight and chest measurement of the fortified group was higher than that of the control group, particularly the increase of weight was more remarkable. The increase in subcutaneous fat, however, showed no difference among the three groups, suggesting that weight gain was probably not due to the increase in the subcutaneous fat of the trunks and limbs but to the muscular and other tissues development promoted by the supplementary substances in diet.From a raise in the Hb value and the number of red blood cells in the experimental group, it was proposed that lysine may be good enough for the prevention or treatment of iron dificiency anemia.So that, to supply meals with lysine between classes was considered to be a simple and convenient means for promoting the health of pupils.