Most cells can exhibit a biochemical pathway which mediates their own destruction in a highly controlled and genetically defined manner. In animal cells, a morphologically distinct form of this 'programmed cell death' has been identified and extensively characterised. This phenomenon, which has been named apoptosis, accounts for most of the cell deaths that take place during the production of biopharmaceuticals from animal cell lines. In the past few years, the factors responsible for the induction of apoptosis in the bioreactor environment have been identified. Furthermore, a growing number of studies have demonstrated that the suppression of apoptosis by the overexpression of anti-apoptosis genes, most notably bcl-2, result in improved culture productivity.