PROJECT SUMMARY/ABSTRACT Background: The homeless population is aging, with an increasing proportion of individuals over age 50 who experience accelerated aging, high rates of mortality, and a high risk of not having their wishes honored at the end of life. Advance care planning (ACP) aims to elicit patients’ medical preferences; yet older homeless adults have low rates of ACP. Significant policy attention has focused on rehousing chronically homeless people into Permanent Supportive Housing (PSH), subsidized permanent housing with voluntary supportive services. Our previous research indicates that PSH may be the ideal setting to initiate ACP; however, no studies have engaged formerly homeless PSH residents in ACP. Our team has created PREPARE for Your Care (PREPARE) – an easy-to-use, evidence-based, online ACP program with video stories. This program includes easy-to-read advance directives, an ACP group visit guide, and an ACP one-on-one facilitation guide. Through a prior R34, we developed a Community Advisory Board (CAB) and together identified preliminary adaptations to PREPARE for the PSH setting. The project requires a final co-development process with formerly chronically homeless older PSH residents and staff and our CAB. The objective of this proposal is to co-develop PREPARE-PSH and compare the effectiveness of facilitated group versus one-on-one visits among formerly chronically homeless older adults in PSH. Aims: We will (1) co-develop PREPARE-PSH with PSH residents, staff, and our CAB; (2) conduct a Hybrid (NIH Stage III efficacy/effectiveness), Type 1, two-arm, cluster randomized trial comparing the effectiveness of two delivery strategies of the PREPARE-PSH program (i.e., ACP movies and easy-to-read ADs) – facilitated group vs. one-on-one visits; and (3) explore implementation- relevant factors associated with ACP engagement and sustainability of ACP in PSH. Methods: In Aim 1 we will engage in a rigorous co-development process through in-depth interviews and focus groups with 20 PSH residents and the CAB. We will use a theory-informed framework (i.e., Behavior Change Wheel (BCW)) and qualitative content analysis to co-create a PREPARE-PSH program. For Aim 2, the CAB noted that groups may be more feasible to scale vs. one-on-one visits and asked us to randomize by site so residents would not feel “left out” of the alternate intervention. Therefore, we will conduct a Hybrid (NIH Stage III efficacy/effectiveness), Type 1 cluster randomized trial comparing delivery of PREPARE-PSH through facilitated groups vs. one-on-one visits using mixed effects models. Randomization will be at the site level, balanced by site size. In Aim 3 we will purposively sample Aim 2 participants for in-depth interviews (n=40-50), conduct focus groups with PSH staff (n=40), and obtain input from CAB members (total n=15). We will explore implementation-relevant factors associated with: (a) high and low ACP engagement and sustainability of PREPARE-PSH using the...