Background: Resident physicians are the direct care providers for many patients with addiction. This study assesses residents' self-perceived preparedness to diagnose and treat addiction, measures residents' perceptions of the quality of addictions instruction, and evaluates basic knowledge of addictions. Methods: A survey was e-mailed to 184 internal medicine residents at Massachusetts General Hospital in May 2012. Results: Responses were obtained from 55% of residents. Residents estimated that 26% of inpatients they cared for met criteria for a substance use disorder (SUD). Twenty-five percent of residents felt unprepared to diagnose and 62% felt unprepared to treat addiction. Only 13% felt very prepared to diagnose addiction. No residents felt very prepared to treat addiction. Preparedness to diagnose or treat addiction did not differ significantly across postgraduate year (PGY) level. Fifty-five percent rated the overall instruction in addictions as poor or fair. Seventy-two percent of residents rated the quality of addictions training as poor or fair in the outpatient clinical setting, and 56% in the inpatient setting. No resident answered all 6 knowledge questions correctly. Slightly more than half correctly identified the mechanism of buprenorphine and 19% correctly answered a question about naltrexone. Nine percent of residents responded that someone had expressed concern about the respondent's substance use. Conclusions: Despite providing care for a substantial population with addiction, the majority of internal medicine residents in this study feel unprepared to treat SUDs. More than half rate the quality of addictions instruction as fair or poor. Structured and comprehensive addictions curriculum and faculty development are needed to address the deficiencies of the current training system.