Effects of temperature on polygalacturonase production by Aspergillus niger VTT-D-86267 were investigated by experiments in a laboratory fermenter. Using a defined medium containing readily metabolizable sugars and purified pectin as carbon source, production of polygalacturonase was most efficient at 18°C and insignificant at 30°C. β-Glucosidase production by the same organism was almost unaffected by temperature between 18°C and 30°C. However, on a technical medium containing less readily available nutrients, production of both enzymes was considerably more efficient at 30°C than at 18°C. The results obtained in this work indicate that productivity of polygalacturonase by A. niger is a function of both temperature and the cultivation medium.