The stability constants of different complex species of some metal ions, viz., Zn2+ and Cd2+ with methylcysteine, were determined electrophoretically at an ionic strength of 0.1 M perchloric acid and at 30-degrees-C. The stability constant of metal-nitrilotriacetate-methylcysteine complexes were found to be 3.72 and 3.54 (log K values) for Zn(II) and Cd(II) complexes, respectively.