The incidence of HIV and (sexually transmitted infections) STI continues to rise in the US among youth, and rates of HIV/STI sexual risk behaviors among adolescents with substance use disorders (SUD) are significantly higher compared with their counterparts without SUD. Yet HIV/STI sexual risk reduction is not regularly implemented within adolescent SUD treatment programs. To address this urgent public health priority, the investigators propose first to develop a manualized sexual risk reduction intervention that 1) builds community clinics' capacity to help families in their care to address systematically adolescents' sexuality; 2) promotes the youths' safer sex practices; and 3) reduces HIV/STI sexual risk behaviors among adolescents with SUD in treatment. Second, the investigators propose to pilot test the manualized intervention to examine feasibility and acceptability of implementation in real-world settings and determine optimal research parameters for such settings in preparation for a randomized clinical trial (RCT). The intervention development process will use a Community Based Participatory Research model of adaptation and development that has been successfully implemented by the PI in other settings. The investigators will conduct formative work to guide adaptation of a multi-family group HIV/STI sexual risk reduction intervention that has demonstrated efficacy with youth, ages 13-18, who have non-SUD psychiatric disorders (Project STYLE: Strengthening Today's Youth Life Experience; R01 MH63008; PI: Brown). This formative work (Phase 1 - protocol 6183) will leverage the research sample of CASALEAP, an ongoing NIDA-funded, large-scale naturalistic study of the effectiveness of outpatient SUD treatment for adolescent (R01 DA019607; PI: Hogue). The resulting new manualized intervention (STYLEnS: STYLE and Substance) then will be pilot-tested (Phase 2 - protocol 6622) with a sample of male and female adolescents with SUD (n=60) in treatment in three well-established New York City mental health outpatient treatment programs which are typical of those for adolescents with SUD and in which the investigators have active partnerships. Pilot participants will be randomly assigned to either STYLEnS or an attention control intervention (Health Promotion). Participants will receive a full-day group intervention on the day of randomization (multi-family, caregivers alone and adolescents alone), return in two weeks for an individual adolescent/caregiver dyad session, and participate in a half-day booster group session three months later. The pilot test will evaluate the feasibility and acceptability of conducting an intervention in outpatient clinics treating adolescents with SUD, examine optimal factors influencing research methods, and estimate intervention parameters for a RCT. Acceptability and feasibility will be assessed using process measures following each session as well as after the intervention is completed. The investigators will assess change in sexual risk behavior outcomes from baseline to 3 months post-intervention. This study will lay the groundwork for refining the design of a RCT of the new intervention. Implementing a HIV/STI sexual risk reduction intervention in clinics providing SUD treatment represents an innovative and potentially cost-effective approach to enable typically overburdened SUD treatment providers to address the heightened HIV/STI risk in SUD youth. This proposal responds to the need to develop HIV/STI sexual risk reduction intervention services for adolescents with SUD that can be applied in and easily disseminated to clinical settings.