ObjectiveAn extracellular proteinase synthesized by the geophilic dermatophyte Microsporum cookei has been purified and characterized. Material and methods The soil isolate of M. cookei was cultivated in modified Czapek-Dox liquid medium containing 0.1% bacteriological peptone and 1% glucose as the nitrogen and carbon sources. Purification of the proteinase was accomplished by (NH4)2SO4 precipitation, followed by ion-exchange chromatography. Results Analysis of the enzyme by SDS-PAGE revealed a single polypeptide chain with an apparent molecular mass of 33 kDa. A keratinolytic activity was evidenced for the enzyme by the keratin azure test. The inhibition profile and the good activity of the enzyme towards the synthetic substrate N-succinyl-Ala-Ala-Pro-Phe-p-nitroanilide suggested that it belongs to the subtilisin group of serine proteinases. Conclusion The keratinolytic properties of M. cookei suggest that this fungus may be an alternative for the recycling of industrial keratinic wastes.