Glycolytic oscillations can be induced by adding glucose to starved Saccharomyces cerevisiae cells and, after a steady state has been established, cyanide. Transient oscillations or limit-cycle oscillations can be induced depending on the growth phase in which the cells are harvested. To find what causes these differences in the dynamic behaviour, we analyzed glycolytic enzyme activities at different growth phases. The hexokinase activity increased by a factor of three after growth substrate transition from glucose to ethanol; the other measured activities remained constant. Cyanide was found not only to block respiration, but also to trap acetaldehyde. Both cyanide actions appear necessary for the occurrence of sustained glycolytic oscillations.