The aim of this work is to develop an active packaging material in which the active compound, lysozyme, is completely immobilized onto the polymeric material and acts directly from the film without being released into the packed foodstuff. Cross-linked films of polyvinyl alcohol, differing in the amount of both antimicrobial and binding agents, were prepared. In order to determine the amount of active substance completely bonded to the polymer backbone, lysozyme release tests were run. The antimicrobial activity of the developed active films was investigated in order to verify their effectiveness in controlling microbial spoilage. A modified version of Gompertz equation was used to quantitatively determine the antimicrobial activity of the films. Results indicate the developed active films are effective in inhibiting the growth of selected microorganism, and that the antimicrobial activity of the investigated films increases as the amount of enzyme incorporated increases. (c) 2005 Elsevier Ltd. All rights reserved.