The inky cap, Coprinellus congregatus, produces mushrooms which become autolyzed rapidly to generate black liquid droplets, in which no cell wall is detected by microscopy. A chitinase (Chi2) which is synthesized during the autolytic phase of C. congregatus inhibits the growths of Candida al-bicans and Cryptococcus neoformans up to 10% at the con-centration of 10 μg/ml, about 50% at concentration of 20 μg/ml, and up to 95% at the concentration of 70 μg/ml. Upon treatment these yeast cells are observed to be severely de-formed, with the formation of large holes in the cell wall. The two yeast species show no growth inhibition at the concen-tration of 5 μg/ml, which means the minimum inhibitory concentrations for both yeast species are 10 μg/ml under these experimental conditions.