A proteinase was purified from the human pathogenic fungus Aspergillus fumigatus. The four chromatographic steps, a “negative” dye column, a “positive” dye column, hydroxyapatite Ultrogel, and modified TSK gel (HW 55), gave a 14% overall yield. The protein migrated as a single band on SDS-PAGE and isoelectric focusing, with an Mr of 82,000 and a pI of 5.6. Inhibitor studies suggested that the enzyme was a metalloproteinase. It hydrolyzed phenylazobenzyloxycarbonyl-Pro-Leu-Gly-Pro-Arg and cleaved native rat type I collagen. © 1994 Academic Press. All rights reserved.