The response of glucose- or nitrogen-limited chemostat cultures of an industrial strain of Penicillium chrysogenum to a period of oxygen starvation was assessed. Indicators of autolysis and morphological changes were monitored quantitatively using a computerised image analysis system. Despite previous reports that O-2 starvation was a likely contributory factor bringing about the onset of autolysis, levels of the indicators of autolysis were modest in this study during and following the anoxic period. Indeed, the cultures remained active at a much reduced level following anoxia, for a length of time dependent on the nature of the nutrient limitation previously imposed. The recovery of cultures from variable periods of anoxia was examined by inoculating aliquots of the bioreactor culture into shake flasks with fresh, complete medium; no recovery or autolysis was observed after 3 or more h of O-2 starvation when the culture (from either the glucose or nitrogen limited chemostat) was inoculated into shake flasks. However, culture survival, as assessed by regrowth after a period of anoxia, was dependent on the nature of the limiting nutrient before anoxia, with N-limited cultures showing improved survival relative to C (energy limited), This study clearly identifies the processes of cell death (cessation of metabolic activity) and cellular autolysis as distinct phenomena.