In the past decade it has been established that regulatory T cells (Tregs) play a major role in the control of all immune responses. As the induction and effector mechanisms used by Tregs are being unraveled, it is emerging that a reciprocal population of CD4⁺ T lymphocytes exists in the immune system that produces inflammatory cytokine IL-17, and coined “Th17 cells”. Th17 cells have been implicated in the pathogenesis of many forms of human disease. This conference will bring together world class leaders in the field to discuss the most up-to-date information on the development, function, mechanism of action, and homeostasis of Tregs and Th17 cells, and the reciprocal control between Tregs and Th17 cells. Several presentations will highlight the results of current clinical trials of Tregs for immune intervention in cancer, autoimmune disease, allergy, and in the induction of transplantation tolerance.