Formation of binary and ternary complexes of Cd (II) metal ion with Efavirenz as a primary ligand and some amino acids (DL-alanine, glycine, Lglutamic acid, DL-isoleucine, DL-methionine, DL-β-phenyl alanine, DL-serine and DL-valine) as secondary ligands was studied by the potentiometric technique at 27±0.1°C in 20% (v/v) ethanol water medium and at 0.1M (NaClO4) ionic strength. Proton ligand (pK) and metal-ligand (logK) stability constant were determined by using Calvin Bjerrum titration technique as modified by Irving & Rossotti. The stability constants of these 1:1:1 ternary complex have been evaluated by the computational methods. that ternary complexes are less favoured than binary complexes.