The ability of intact cells of three strains of Saccharomyces to degrade haemoglobin at pH 3.7 increased during sporulation in acetate medium. The highest proteolytic activity was found approximately 17 hours after transfer to sporulation medium, at which time a large percentage of the cell population was in the tetranucleate stage just before the appearance of spore walls. Three non-sporogenic strains showed no change in proteolytic activity. On the basis of permeability relationship and the absence of activity in sporulation medium from which the sporulating cells were separated, the writers suggest a peripheral location of the enzyme, apparently the first such report for a yeast proteinase.