Laccase, aryl-alcohol oxidase and superoxide radicals were detected in ligninolytic cultures of Fusarium proliferatum. Enzyme activities were present during the secondary metabolism and seen as Single protein bands after non-denaturing electrophoresis. In contrast, superoxide radicals were detected during primary growth, correlating with maximal lignin mineralization, Moreover, ligninolysis decreased when scavengers of both superoxide and hydroxyl radicals were added to cultures, indicating that activated oxygen species are involved in lignin degradation.