PROJECT SUMMARY/ABSTRACT The Diabetes Prevention Program (DPP) helps patients with prediabetes initiate lifestyle changes and delay or prevent T2DM. However, the DPP has been most successful in middle-class populations. The Centers for Disease Control and Prevention (CDC)-supported National Diabetes Prevention Program achieved widespread implementation but had limited reach and effectiveness in low-income communities. In a major step forward, California has mandated in Senate Bill 97 that as of January 1, 2019, all eligible Medicaid (e.g., Medi-Cal) beneficiaries who want to enroll in the DPP must be provided this opportunity. The outcomes of SB 97 will have major implications on diabetes prevention for Medicaid beneficiaries not only in California but also across the US. We are proposing an evaluation of SB 97 using data from Kaiser Permanente Northern California (KPNC) and the University of California, Los Angeles (UCLA). Using advanced analytic approaches, we will evaluate the effects of this natural experiment on clinical outcomes. We will also collect important contextual primary data from the 43 CDC-recognized or pending DPP suppliers in California, and from both DPP lifestyle coaches and DPP participants. Our Specific Aims are as follows: 1) To determine the effectiveness of SB 97 and mandated Medi-Cal DPP coverage on change in body weight (primary outcome), systolic blood pressure (SBP), uptake of the DPP in- person or online, and projected future cost savings (all secondary outcomes) among Medi-Cal beneficiaries with prediabetes at KPNC and UCLA, versus a comparison cohort of patients with insurance coverage from the California Health Insurance Exchange (HIE). 2) To characterize perspectives from leaders of CDC-recognized DPP suppliers including decisions about providing DPP to Medi-Cal beneficiaries, such as their processes of identifying the target population, raising awareness of and promoting the DPP, and recruiting and enrolling eligible participants. 3) To characterize perspectives of Medi-Cal DPP participants and DPP lifestyle coaches on facilitators and barriers to participant retention and engagement. Our team includes a collaborative group of health services researchers, a statistician, and a health economist with experience in program evaluation and outcomes research, who have a longstanding working relationship. If funded, we are well positioned and ready to initiate the proposed policy evaluation in the post-enactment period.