07. Project Summary The goal of this proposal is to identify strategies to improve the effectiveness and sustainability of overdose education and naloxone distribution (OEND) programs for people who use drugs (PWUD). Research suggests that some PWUD enthusiastically take up the role of “overdose responder”, responding to multiple overdoses over relatively short periods of time. Others, however, respond to few or no overdoses. We seek to determine the individual, social network, and contextual factors that influence overdose response behavior, with the goal of improving support for PWUD who respond to multiple overdoses and identifying intervention targets to improve the overall capacity of PWUD networks to respond to overdoses among their members. To answer these questions, we propose a longitudinal mixed methods study with 300 PWUDs recruited in Reno, Nevada (an understudied Western region), to address the following aims: 1. Identify the individual, social network, and contextual characteristics of OD responders (relative to those who do not carry or do not use the naloxone they have), including substance use behaviors, size and composition of social networks, personal resilience factors, and geographic and socio-structural factors. 2. Qualitatively describe the positive and negative experiences of responding to ODs, and identify (a) the support or services needed by PWUDs to sustainably respond to ODs in their communities, and (b) the barriers to response among those who do not respond or stop responding. 3. Assess feasibility and acceptability of interventions to improve sustainability and wellbeing of responders, and increase initiation of response behavior among non-responders. Supplemental Aim: Collect quantitative and qualitative data to inform an agent-based model (ABM) of PWUD to test how different OEND program delivery strategies could lead to reductions in fatal OD rates.