Cell suspension culture of C. roseus in a stirred-tank bioreactor was subjected to a 6 h anaerobic period at intervals of 42 h. The anaerobic treatments resulted in the inhibition of cell growth, a reduction in cell viability, and an increase in the pH of medium and ethanol production. However, the injured responses to anaerobiosis could recover to varying degrees when the culture was transferred to aerobic conditions, indicating that no permanent, irreversible injury to the culture has been caused by the short anaerobic period (6 h). The activities of secondary metabolism, the production of ajmalicine and catharanthine, reacted to anaerobic stress in different ways. Anaerobic stress did not significantly affect ajmalicine production but triggered the biosynthesis of catharanthine. Anaerobic stress stimulated the release of these alkaloids from cells into the medium.