The formation constants of the species formed in the systems H+ + dioxovanadium(V) + penicillamine and H+ + penicillamine have been determined in aqueous solutions of methanol at 25 degreesC and constant ionic strength, using spectrophotometric and potentiometric techniques. It was shown that dioxovanadium(V) forms two mononuclear 1:1 and 1:2 complexes with penicillamine. The formation constants in various media were analyzed in terms of Kamlet and Taft's parameters. Single-parameter correlation of the formation constants, beta(121), and beta(142), versus alpha (hydrogen-bond donor acidity) and beta (hydrogen-bond acceptor basicity) is poor in all solutions, except for pi* (dipolarity/polarizability), but multiparameter correlation represents significant improvement with regard to the single-parameter models. Linear relationships are observed when log beta(121) and log beta(142) are plotted versus pi*. Finally, the results are discussed in terms of the effect of the solvent on complexation.