PROJECT ABSTRACT OPTIMUM (Optimizing Pain Treatment In Medical settings Using Mindfulness) is a pragmatic clinical trial (PCT) of mindfulness-based stress reduction (MBSR) for chronic low back pain (cLBP) delivered via telemedicine. Despite evidence of effectiveness for MBSR at decreasing pain and improving function, it remains underutilized and has not been embedded into routine clinical care. To address barriers to integration of MBSR in primary care and determine MBSR effectiveness in real-life settings, we are conducting OPTIMUM in three sites: the largest safety net hospital in New England, federally qualified health centers in North Carolina and a large academic health center in Pittsburgh. These sites serve large numbers of underserved people as well as a diverse patient population. For OPTIMUM to be successful it is imperative that participants, clinics, and relevant stakeholders be fully engaged in the program, and that recruitment is timely and successful. Through this supplement we will significantly expand patient and stakeholder engagement to fully address recruitment and retention issues as well as future dissemination efforts. In Aim 1, we will expand the OPTIMUM Community Advisory Board (CAB) to include more patients, clinical personnel, healthcare administrators, and advocacy group and mindfulness organization representatives.The CAB will meet monthly throughout the course of the trial, and members will receive training to increase their effectiveness as stakeholders. In Aim 2, persons with cLBP enrolled in the OPTIMUM trial will be recruited to participate in quarterly focus groups to provide their perspectives on strategies to improve recruitment and retention. To increase the breadth of stakeholders that provide perspectives on engagement efforts, we will interview a range of multi-level stakeholders, including providers, pain advocacy groups, healthcare administrators, and payors. In Aim 3 we will partner with Story Booth (a project led by the Path Towards a Learning Health System network) to obtain perspectives from persons with cLBP not participating in the study. These stories will inform our trial engagement efforts as it is expected that hearing a larger number of voices, including Spanish-speaking patients, will result in the identification of additional barriers to recruitment and implementation. Our approach is informed by principles of Community-Based Participatory Research, to promote greater sustainability as well as community acceptance of OPTIMUM. Continuous data analysis will inform an iterative process to refine protocols, optimize recruitment, maximize retention, and prepare for future implementation and dissemination.