Induction of immunity and peripheral tolerance requires contacts between antigen-bearing dendritic cells (DCs) and cognate T cells. Using real-time two-photon microscopy, we have analyzed the dynamics of CD8⁺ T cells in lymph nodes during the induction of antigen-specific immunity or tolerance. At 15–20 h after the induction of immunity, T cells stopped moving and established prolonged interactions with DCs. In tolerogenic conditions, despite effective initial T cell activation and proliferation, naive T cells remained motile and established serial brief contacts with multiple DCs. Thus, stable DC–T cell interactions occur during the induction of priming, whereas brief contacts may contribute to the induction of T cell tolerance.