The oxidoreductive enzyme laccase (E.C.1.10.3.2.) isolated from a culture medium of white-rot fungus Trametes versicolor transformed lignin preparations solubilized in a dioxane-H2O (7:3) mixture. The obvious net result of lignin transformation was an increase in molecular mass. A superoxide radical was found in the reaction mixture during lignin incubation with laccase. It appeared that a change in the reaction medium or in the lignin molecule instigated by laccase could lead to polymerization after the lignin molecules had crossed a dialysis membrane and were separated from the enzyme. Two possible mechanisms are suggested, either diffusion of an activated oxygen species or diffusion of primed lignin molecules. Laccase was able to co-polymerize lignin with low-molecular-mass compounds of different origins, particularly with aromatics containing either carboxyl or isocyanate groups, as well as acrylamide - an aliphatic monomer containing a vinyl group.