pH-metric investigation on the complex formation equilibria of Co II, NiII, CuII and ZnII (M II) with anthranilic acid N,N-diacetic acid (H3ada) in the absence and presence of 1.10-phenanthroline (phen), bipyridine (bipy), ethylenediamine (en), glycinate (gly-) and oxalate (ox2-) (B) in aqueous solution at 25 ± 1° at a fixed ionic strength, I = 0. 1 M (NaNO3) indicates the formation of simple binary complexes M(ada) and M(B) and ternary complexes M(ada)(B). M(ada)(B) complexes are formed according to equilibria M(B) + adaH ⇋ M(ada)(B) + H, with B = phen and bipy, and M(ada) + BH ⇋ M(ada)(B) + H, with B = en, gly- and ox2- ligands. Stability constants of the complexes have been evaluated by computerized method.