The presence of chitinase activity without inducers in the enzymic precipitates from the culture fluid of 25-day-old autolyzed cultures of 17 Fusarium species has been studied. In all cases endochitinase and beta-N-acetylglucosaminidase activities were found. The chitinase activity as a joint action of these two enzymes with production of N-acetylglucosamine was also determined. A correlation among endochitinase, beta-N-acetylglucosaminidase, and chitinase was always found. Fusarium oxysporum f.sp. lini, F. subglutinans, and F. moniliforme were the best producers of chitinase activity. Fusarium species could be a good source of chitinases for production by fungi.