Adaptive radiotherapy has been an advancing topic of research since the late 1990s when Yan et al published the first article discussing the mathematical concept and potential benefits of this approach. 1 Nine years ago, adaptive radiotherapy was the topic of Seminars in Radiation Oncology. In his introduction, Dr. Yan, the special editor of the issue, described the potential improvements in clinical treatment outcomes reported in the issue to be "extremely encouraging and greatly promote adaptive radiotherapy." 2 It is timely to evaluate, nearly a decade later, how far we have come in advancing adaptive radiotherapy in the clinic and what new emerging technology is opening new doors. The goal of this issue of Seminars in Radiation Oncology is to discuss the current status and future directions in adaptive radiotherapy. The issue specifically focuses on advances in the tools needed for adaptive radiotherapy, including autosegmentation, deformable registration, and automated planning, advances in workflows, including offline, real-time, functional, and anatomical, and evidence of benefit in clinical sites, including head and neck, lung, and cervix.