The stability constant on complexation of VO2+ with alanine in mixed solvent systems of methanol + water and ethanol + water have been determined spectrophotometrically at 25 +/- 0.1 degrees C and I = 1 mol.dm(-3) of sodium perchlorate as ionic medium in the pH range 1.3-2.3, with high ligand-to-metal ratios. Linear relationships are observed when log K is plotted versus 1/D, where K and D represent stability and dielectric constants of the system, respectively. Also, the results are discussed in terms of the effect of solvent on protonation and complexation.