ABSTRACT: More than 20 years ago, even before voters in Oregon had enacted the first aid in dying (AID) statute in the United States, Timothy Quill and colleagues proposed clinical criteria AID. Their proposal was carefully considered and temperate, but there were little data on the practice of AID at the time. (With AID, a physician writes a prescription for life-ending medication for a terminally ill, mentally capacitated adult.) With the passage of time, a substantial body of data on AID has developed from the states of Oregon and Washington. For more than 17 years, physicians in Oregon have been authorized to provide a prescription for AID. Accordingly, we have updated the clinical criteria of Quill, et al., based on the many years of experience with AID. With more jurisdictions authorizing AID, it is critical that physicians can turn to reliable clinical criteria. As with any medical practice, AID must be provided in a safe and effective manner. Physicians need to know (1) how to respond to a patient's inquiry about AID, (2) how to assess patient decision making capacity, and (3) how to address a range of other issues that may arise. To ensure that physicians have the guidance they need, Compassion & Choices convened the Physician Aid-in-Dying Clinical Criteria Committee, in July 2012, to create clinical criteria for physicians who are willing to provide AID to patients who request it. The committee includes experts in medicine, law, bioethics, hospice, nursing, social work, and pharmacy. Using an iterative consensus process, the Committee drafted the criteria over a one-year period.