The stability constants or the reaction of dioxovanadium(V) with ethylene glycol-bis(2-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA) and the dissociation constants of EGTA were determined at 25 degrees C and a constant ionic strength of 0.05 mol.dm(-3) sodium perchlorate in ten different compositions of water + methanol by a combination of potentiometric and UV spectrophotometric methods. The Solver, Microsoft Excel 2000 optimization package. has been used to perform nonlinear least-squares curve fitting on the basis of the Gauss-Newton method for calculation of the solvatochromic regression coefficients. Nonspecific and specific solute-solvent interactions were interpreted by correlating the equilibrium data with solvent parameters using the Kamlet-Abboud-Taft (KAT) solvatochromic equation. Finally, the influence of the solvent on the stability of the complex) was discussed On the basis of the correlation results and the contribution of alpha (hydrogen-bond donor acidity), beta (hydrogen-bond acceptor basicity), and pi* (dipolarity/polarizability) parameters.