This protocol is to evaluate the degree to which a combined group and individual 12-Step facilitative (TSF) intervention, Stimulant Abuser Groups to Engage in 12 -Step (STAGE-12), improves substance -related outcomes compared to treatment as usual (TAU) without STAGE-12 among stimulant abusers. The primary objective is to evaluate reduction in percent of days of stimulant use as measured by self-report. Secondary objectives include evaluating reduction in percent days of use of other substances, the degree to which STAGE-12 increases involvement in 12-step activities and attendance at 12-step meetings, and the extent to which such 12 -step involvement and meeting attendance mediate substance use outcomes.