This paper from the California Health Care Foundation reviews recent changes to the Confidentiality of Alcohol and Drug Abuse Patient Records, 42 Code of Federal Regulations (42 CFR Part 2) related to substance addiction treatment. The opioid epidemic has prompted efforts across the country to increase the availability of treatment, and primary care practices have taken a more prominent role in providing care for patients with substance addictions. This comes at a time when the delivery system for substance addiction care overall is evolving as states and providers aim to break down treatment silos and encourage care to be integrated with other forms of health care, including physical and mental health services. A common roadblock for these practices is federal confidentiality rules, which can make effective information sharing a challenge because providers must balance the privacy protections in 42 CFR Part 2 with their efforts to coordinate care. The report analyzes how 42 CFR Part 2 applies to primary care practices that seek to expand access to treatment, and how providers in different parts of the country are navigating these rules.