The primary aim of this two-group community-based, randomized controlled trial was to assess the efficacy of adherence-focused MI to help homeless smokers quit smoking. Once eligibility was determined, participants were randomized to either the intervention arm (NRT + MI) or to the control arm (NRT + standard care (SC)). At baseline, participants in both groups received a 2-week supply of 21-mg NRT patches [25 (link)], selected based on preferences expressed in preliminary studies [15 (link),18 (link)]. For the initial 8 weeks of the study, participants in both arms received an additional 2-week supply of nicotine patch every 2 weeks. They were instructed on how to use the patch daily; any concerns were addressed by research staff. In addition, participants randomized to the intervention arm received six MI counseling sessions, 15–20 min in length, while participants randomized to the SC arm received one brief session (10–15 min long) of advice-oriented counseling to quit smoking. The brief directive advice was designed to simulate a typical clinical encounter. The design did not include a placebo arm due to ethical concerns as well as the communal living situation of homeless people (i.e., the possibility of participants in different study arms sharing patches could lead to contamination of study groups). The primary outcome was biochemically verified smoking cessation assessed at 6 months postrandomization. Participants who did not return for the 6-month assessment were classified as treatment failures. The secondary outcome was adherence to NRT. Additional aims included identifying the potential moderating effects of substance abuse, psychiatric comorbidities, and other demographic and smoking behavior variables on intervention efficacy.