Synchronous cultures prepared by selection from an elutriating rotor were used to measure activity changes during the cell cycle of the following enzymes: acid phosphatase in Schizosaccharomyces pombe and Saccharomyces cerevisiae, alpha-glucosidase in S. cerevisiae and beta-galactosidase in Kluyveromyces lactis. There was no sign of step rises in activity in acid phosphatase but there were indications in S. cerevisiae of the linear pattern with rate doublings once per cycle that had been found previously in S. pombe. There was also no sign of step rises in the other two enzymes, in contrast to earlier results using different techniques. Asynchronous control cultures showed little or no perturbations after the first hour.