Dr. Fiellin has focused his scholarly work on the interface between primary care, general healthcare settings and addiction. He is a primary care internist Board Certified in Addiction Medicine. He serves as the inaugural Director of the Yale Program in Addiction Medicine. He conducts research on the transfer of treatments for opioid use disorder and alcohol use disorder from specialized settings to office-based, primary care, Emergency Department and HIV specialty settings. He has served as Principal Investigator on multiple NIH-funded research clinical trials, observational studies and implementation science. He has received awards from the American Association for the Treatment of Opioid Dependence, the American Society of Addiction Medicine, AMERSA and the the Hazelden-Betty Ford Foundation. He is on the Editorial Boards of the Journal of Addiction Medicine, Journal of Substance Abuse Treatment, and Substance Abuse and is Co-Editor of Alcohol, Other Drugs & Health: Current Evidence and the Principles of Addiction Medicine, 4th, 5th and 6th Editions. He has served on the Board of Directors of the College on Problems of Drug Dependence and as Co-Chair of the Substance Abuse Task Force for the Society of General Internal Medicine.