The concentration of free amino acids and their related compounds has been determined in the lenses of ICR (f) strain rat and in the Wistar strain rat's lenses which were cultured with diethyl maleate. It was supposed that the decrease of cystathionine and the increase of serine in lenses of ICR with aging were related with development of senile cataracts. The increase of cystathionine in lenses cultured were suggested that synthesis of taurine is done by cystathionine pathway. Quantitative changes of amino acids were higher than normal of glutamine, glycine and aspartate in lenses cultured. It was supposed that the changes were the flow in lens from medium for synthesis of glutathione and glucose.