Formation of mixed ligand complexes of Zn(I1) with NTA, EDTA and HEDTA as primuy ligands and glutamic acid as a secondary ligand has been studied potentiometrically. The -KMLA values are larger than K l:' and K2 values of simple Zn(II) - glutamate chelates. Further the stability sequence with respect to primuy Ugands is EDT A > HEDT A > NT A.