Possible impact of protozoan PCD pathways in parasite biology and life-or-death decisions. Parasitism depends on check points that control the population of the parasites and the survival of the host. In this sense, the existence of different PCD mechanisms in protozoan parasites appears to be crucial and may regulate distinct biological processes that are decisive for the outcome of infection. From a physiological point of view, PCD pathways can determine cell densities and differentiation at least under certain conditions, both processes being inter-connected by the regulated cross-talk between apoptotic and autophagic pathways. On the other hand, the involvement of autophagy on organelle remodelling allows the parasites to accomplish their complex life cycles and to adapt to different environments. Regarding the parasite-host interaction, several parasites are able to dampen immune responses and colonize the different environments in the hosts using apoptotic signalling. Deregulation of these processes can lead to activation of a predominant death signalling pathway that might be used as an attractive therapeutic strategy.