Department of Chemistry, University College of Science, 92 Acharya Prafulla Chandra Road, Calcutta-700 009 Manuscript received 17 May 1988, revised 11 January 1989, accepted 23 February 1989 pH-metric study on the complexation equilibria of CoII, NiII and ZnII (M2+) with some salicyloylamino acids, (o)HO C6H4C(-O)NHCH(R)COOH) or (H2L), where R=H (salicyloyl glycine), CH2 (salicyloyl dl-α-alanine), CH2CH2SCH2 (sail­cyloyl dl-methionine), provided evidence of formation of ML, \(ML^{2-}_2\)- and ML(OH)­complexes through bidentate (O,\(\bar{O}\)) chelation by the amide carbonyl oxygen atom and phenolate oxygen atom of the ligand, leaving the carboxylate group uncoordinated in these complexes. Formation constants at 25±0.1° in 50% (v/v) aqueous ethanol medium and ionic strength µ = 0 2 M (NaNO2) were in the order. CoII < NiII < znII for the ML and \(ML^{2-}_2\) complexes, in the order CoII > NiII > ZnII for the M(OH) (L)- complexes with all the three ligands, and in the order, salicyloylglycine > salicyloyl-dI- \(\propto\)-atanine > salicyloyl dl-methionine for all the three metal ions. The results have been correlated with the modes of bonding of the ligands in the resulting complexes and compared with the corresponding values of the complexes formed by CuII.