BACKGROUND: The availability of the fellowships of Alcoholics Anonymous and Narcotics Anonymous in community settings is extensive and patients admitted to treatment programs for substance use disorder may therefore have previously attended meetings of these two Twelve Step (TS) programs. Data on such prior attendance and related clinical findings, however, are not typically available. They can, however, be relevant to how ensuing treatment is planned. We therefore undertook this study to ascertain the feasibility of evaluating how the level of TS attendance prior to treatment entry can be evaluated, and to determine clinically relevant findings that are associated with such attendance. METHODS: Over the course of 2022, 3,125 patients were admitted to a large urban multimodal United States-based treatment center. All patients were administered the structured interview-based Global Appraisal of Individual Needs upon admission. This instrument is employed to evaluate substance use, demographics, and related psychosocial variables. Clinically related variables were analyzed relative to whether given respondents have a history of any TS group attendance prior to admission. RESULTS: Distinctions were found between the 57.3% of respondents who had previously attended any TS meetings and the 42.6% who had not attended any meetings. Compared to respondents who had never attended TS meetings, those who had ever attended scored higher on emotional problems (p <
.001, d = -0.58), and had more likely undergone previous SUD treatment (p <
.001, d = 0.80). They were less likely to use substances in unsafe situations (p <
.001, d = -0.55) and were less likely to express reluctance to remain abstinent (p <
.001, d = -0.50). The 11% of respondents who considered themselves regular TS members reported a lower frequency of recent substance use (p <
.001, d = -0.80) and were more likely to have attended intensive outpatient (p <
.001, 0.46) and residential (p <
.001, 0.44) treatment than patients who did not consider themselves regular attenders. CONCLUSIONS: Examination of TS attendance prior to treatment admission is feasible. Findings can be clinically relevant for differential treatment planning and can also serve as a basis for further research into the role of TS participation in community settings.