An extracellular chitinase from Streptomyces halstedii AJ-7, a broad spectrum antifungal biocontrol agent, was characterized and purified. The apparent molecular weight of the purified protein was 55 kDa, K-m value and V-max of the protein for colloidal chitin were 3.2 mg ml(-1) and 118 mu mol h(-1), respectively. The growth and chitinase activity of S. halstedii AJ-7 were enhanced by adding of 0.1% killed mycelium of Fusarium oxysporium in a medium containing 0.2% colloidal chitin.