We propose a 3-year study to develop and pilot test a social network substance use and HIV-risk intervention for permanent supportive housing program residents in the Skid Row area of Los Angeles. The intervention will be developed for residents at the Skid Row Housing Trust (SRHT), one of the largest Housing First providers in Los Angeles. Housing First residents are not required to abstain from alcohol and drugs as a requirement of their residency. There is some evidence that providing housing rapidly to chronically homeless persons--along with support--helps to reduce substance use and HIV risk behaviors in the short term because homelessness is the primary cause of high-risk behavior. However, the evidence thus far is limited. One aspect that has not received much research attention is the needs of Housing First residents for support to transition their social networks while transitioning out of homeless into residency in a Housing First program. New residents are exposed to a wide range of potentially negative social influences while also having greater potential to reconnect with lost positive ties. This project will develop a social network intervention to residents of SRHT in order to increase their knowledge about their social networks and enhance their motivation to make necessary changes to improve their ability to reduce or continue to abstain from high-risk behavior. The intervention sessions will enhance the weekly support meetings that SRHT case workers already conduct with new residents during their first 6 months of residency. Case workers will be trained to deliver the 30-minute intervention sessions using a motivational interviewing style. The intervention will be developed so that case managers can deliver it with the aid of an electronic tablet device. The tablet will guide them in collecting information about the residents' social networks and then display several diagrams highlighting various aspects of the residents' networks. They will then use motivational interviewing techniques to guide residents to think about how their network currently functions, how they would like it to function, and what steps they can take to make changes necessary to achieve goals related to reducing their substance use and sexual risk behaviors. The intervention will be delivered by case managers across four sessions (at baseline and at two-week intervals). We anticipate that residents who participate in this intervention will develop new strategies in their interactions with their social networks that will facilitate a reduction in their high-risk behavior.