Cystine Lithiasis occurs rarely in cases of cystinuria, a congenital disorder of amino acid metaboilsm. In this report, we describe 3 cases with cystine lithiasis. Two cases of them were diagnosed as cystine lithiasis by means of component analysis of thire urinaly stones, while the other was diagnosed by means of analysis of amino acid in urine. The method for diagnosis and the treatment of cystinuria are discussed.