BACKGROUND Education about substance use (SU) disorders remains inadequate in medical training. OBJECTIVE To describe the Chief Resident Immersion Training (CRIT) program in addiction medicine and to evaluate its impact on chief resident (CR) physicians' substance use knowledge, skills, clinical practice, and teaching. METHODS A controlled educational study of CRIT programs (2003, 2004, and 2005) for incoming CRs in generalist disciplines. Intervention CRs were trained to diagnose, manage, and teach about SU. The control CRs sought but did not receive the intervention. METHODS Eighty-six CR applicants to the CRIT program. METHODS Baseline and 6-month questionnaires assessing substance use knowledge, skills, clinical practice, and teaching. Outcomes were compared within groups from baseline to follow-up and between groups at follow-up. RESULTS The intervention (n = 64) and control (n = 22) CRs were similar demographically. At 6-month follow-up, the intervention CRs reported a significant increase in SU knowledge, confidence, and preparedness to diagnose, manage, and teach and an increase in SU clinical and teaching practices compared to their baseline and control CRs. CONCLUSIONS This intensive training for chief residents (CRs) improved knowledge, confidence, and preparedness to diagnose, manage, and teach about substance use (SU), affecting both the CRs' SU clinical and teaching practices. The CRIT program was an effective model for dissemination of SU knowledge and skills to educators in a key position to share this training with a broader audience of medical trainees. This model holds potential to address other high priority medical, yet under-addressed, content areas as well.