An entomopathogenic filamentous fungus, Paecilomyces lilacinus strain HY-4, has a great potential as a promising bio-pesticide due to its superior pathogenicity against Adoretus tenuimaculatus and Tetranychus urticae. When the fungal strain infects host cuticle, it secrets a combination of hydrolytic enzymes including chitinase to solubilize the cuticle. Thus, we investigated effects of different carbon and nitrogen sources on the production of a chitinase from P. lilacinus strain HY-4. The organism produced an extracellular chitinase at a relatively high level (45.4 mU/ml) when cultivated for 5 days on a medium supplemented with insect pupa (0.5%) and colloidal chitin (1%), which was prepared by treating chitin from crab shells (Sigma-Aldrich Co. Ltd.) with 12 N HCl solution. However, extracellular secretion of chitinase by strain HY-4 was found to be significantly repressed in the presence of glucose (1%).