Formation constants of chelates of ampicillin, dopamine, and α -methyl L-dopa with Cu2+, Fe3+and Zr4+have been determined in aqueous medium at ionic strength of 0.1 M (KC1) using Calvin-Bjerrum technique as applied by Irving and Rossotti. Zirconium forms relatively more stable chelates with ampicillin as compared to copper and iron. However, in case of dopamine and α-methyl L-dopa the chelation with iron is the more stable. The order of stability of copper and iron is in agreement with the Irving-Villiems order. The mixed ligand chelates have been, also, investigated. The stability sequence has been found to be Cu2+< Fe3+< Zr4+