A series of porous copolymer beads based on the alkyl methacrylate eaters (AMA) was prepared with toluene as inert diluent, and their swelling behavior, mainly in nonsolvents, were investigated. It was found that all these copolymers with relatively high degree of crosslinking do swell in methanol, a nonsolvent for them: and the swelling extent increases and passes through a maximum with an increase in the degree of crosslinking. The incorporation of methacrylic acid (MAA) into the AMA-based copolymers doesn't change the swelling ability of the copolymers in a nonsolvent, but changes the type of solvent as a nonsolvent. Thus copolymers with MAA incorporated present swelling behavior in toluene and in buffer at specific pH's just as in a nonsolvent. From these results we believe that the swelling ability in nonsolvent are characteristic for copolymers with relatively high degrees of crosslinking when prepared in the presence of a large amount of diluent with high solvating power for the polymer. (C) 2000 Elsevier Science B.V. All rights reserved.