Aims: To test the effectiveness of an intervention, Al-Anon Intensive Referral (AIR), to facilitate participation in Al-Anon Family Groups (Al-Anon). Design, Setting and Participants: Multi-site, randomized controlled trial of AIR versus usual care (UC), with follow-up assessments at 3, 6 and 12 months. The 12-month follow-up rate was 74%. Residential alcohol use disorder (AUD) treatment programs in three US locations. Concerned others (COs) of patients in treatment for AUD. COs were mainly women (77%) who were patients' spouses (33%) or parents (25%). Intervention and Comparator: AIR (n = 128) consisted of four sessions over 3 months with an Al-Anon coach. UC (n = 151) was the treatment program's offer of educational sessions for COs. Measurements: Primary outcome: COs' self-reports of any Al-Anon attendance (yes or no) at 3 months. Secondary outcomes: number of Al-Anon meetings and the CO-patient relationship (stressors, resources). Potential predictors of outcomes examined in generalized linear mixed models were their baseline value, time, CO-patient relationship type (marital or non-marital), treatment program and condition.