Thermometric titrimetry has been employed to determine K, ΔH⊖, and ΔS⊖ data for the complexation reaction in aqueous solution of ethylenediamine-NN′-diacetic acid, trimethylenediamine-NN′-diacetic acid, ethylenediamine-NN′-di-α-propionic acid, and NN′-dimethylethylenediamine-NN′-diacetic acid with alkaline-earth metal cations. Factors influencing the thermodynamic stability of these complexes are discussed.