Cytotoxic (CD8+) and helper (CD4+) T cells play a crucial role in resolving infections by intracellular pathogens. The development of technologies to visualize antigen-specific T cell responses in mice and men over the past decade has allowed a dissection of the formation of adaptive T cell immunity. This review gives a brief overview of the currently used detection techniques and possible future additions. Furthermore, we discuss our current understanding of the formation of antigen-specific T cell responses, with particular attention to the similarities and differences in CD4+ and CD8+ T cell responses, the functional heterogeneity within responder T cell pools and the regulation of CD8+ T cell responses by dendritic cells and CD4+ helper T cells.