Summary The importance of regulatory T lymphocytes (Tregs) in the control of autoimmunity is now well established in a variety of experimental animal models. In addition, there are numerous studies suggesting that Treg deficits may be an underlying cause of human autoimmune diseases. The emergence of Tregs as an essential component of immune homeostasis provides a potential therapeutic opportunity for active immune regulation and long-term tolerance induction. In this article, we summarize the core basic science and animal model studies of Tregs, review the status of multiple biologic and small molecule chemical compounds to promote Treg development in vivo, and discuss recent advances for the identification and expansion of polyclonal and antigen-specific Tregs for adoptive immunotherapy. In summary, the review provides an in-depth analysis and highlights the challenges and opportunities for immune intervention with Treg-based therapeutics.