The bcl-2 family of proteins play an important role in the control of apoptosis. Family members exist which are either pro- or anti-apoptotic and their activity appears to control a checkpoint between signals from the cell surface and activation of the ICE-family of proteases. Despite having a key role to play in apoptosis, the mechanism of action of these proteins can only, at present, be inferred due to the lack of understanding about their biological activity. However, some general principles can be gleaned from the large boby of published work to suggest what are likely to be the best directions for future endeavour.