Cytotoxic T-lymphocytes (CTL) are famous for their ability to kill tumor, allogeneic and virus-infected cells. However, an emerging literature has now demonstrated that CTL also possess the ability to directly recognize and kill bacteria, parasites, and fungi. Here, we review past and recent findings demonstrating the direct microbicidal activity of both CD4(+) and CD8(+) CTL against various microbial pathogens. Further, this review will outline what is known regarding the mechanisms of direct killing and their underlying signalling pathways.