The entomopathogenic fungusBeauveria bassianaproduces two extracellularN-acetylglucosaminidases (NAGase) in liquid medium containing colloidal chitin as the sole source of carbon and nitrogen. To study the regulation of NAGase synthesis,N-acetyl-D-glucosamine (GlcNAc), glucose NH4NO3, or amino acids were added to the colloidal chitin medium and NAGase activity was measured. NAGase synthesis was (i) induced with GlcNAc, and no repression was observed with GlcNAc provided at 2% (w/v); (ii) repressed in the presence of glucose plus NH4NO3; (iii) partially repressed when glucose or NH4NO3was provided; and (iv) repressed to levels that were < 40% of the control levels when glutamic acid, tyrosine, arginine, proline, valine, and histidine were provided to the colloidal chitin medium. Total NAGase activity levels were > 60% of the control activity when alanine, glycine, isoleucine, aspartic acid, and leucine were tested. It appears that synthesis of NAGase is sensitive to cell energy and the carbon and nitrogen requirements.Key words:Beauveria bassiana,N-acetyl-D-glucosaminidase, entomopathogenic fungus, extracellular enzyme, regulation.