Biocompatible copolymers of N-vinylpyrrolidone (P) and furfuryl methacrylate (F) were prepared by free radical polymerization in N,N-dimethylformamide solution at 50 degrees C, using 2,2'-azobisisobutyronitrile as initiator, at low and high conversion. The microstructure of copolymers prepared at low conversion was determined from the composition data by the application of statistical relationships, considering the terminal copolymerization model of Mayo-Lewis, whereas for high conversion copolymers the noticeable difference between the reactivity of F and P was taken into consideration. The swelling behaviour of films prepared from solutions of copolymers with different composition was followed gravimetrically and the diffusion of water was analysed on the basis of the stress relaxation model of copolymer chains. The results obtained are in good agreement with second-order diffusion kinetics, showing that the hydrophilic character of the films is controlled mainly by the content of P in the copolymer systems and the distribution of comonomeric units along the copolymer systems.