Enzymatic activities of proteinases A and B, carboxypeptidase Y, and aminopeptidase I, vacuolar enzymes in beer yeast, Saccharomyces cerevisiae, were measured at different stages of growth in the synchronous culture. All enzymatic activities fluctuated synchronously during the cell growth in a periodical cycle. The maximum activities were observed before cytokinesis and the minimum activities were found just after completing cytokinesis.