PROJECT SUMMARY People with diabetes are at high risk of developing a range of diverse microvascular, macrovascular and neuropathic complications that are associated with high morbidity and erode their quality of life. Diabetes is expected to take an increasingly large financial toll in in the United States (U.S.) the future, particularly among working age adults. Ongoing, timely and efficient surveillance of type 1 and type 2 diabetes diagnosed among young adults aged 18-45 years is essential to identify health disparities and inform health care systems and the public health community to identify and prioritize strategies to prevent diabetes and its complications. The Colorado DiCAYA surveillance team is ideally situated to address the critical challenge of utilizing existing electronic data sources to generate accurate, timely estimates of the incidence and prevalence of diabetes among the young adult population by type, age, sex, and race/ethnicity subgroups. In response to RFA-DP-20- 001- Component B, we propose to ascertain the annual prevalence and incidence of diabetes among adults aged 18-45 years of age in the state of Colorado starting with year 2020 from the following data sources: 1) electronic health records from the well-established SEARCH network of endocrinology clinics, community clinics and hospital networks in Colorado; 2) a state-wide, legislatively mandated All Payers Claims Database that contains over 33 commercial health plans and 100% of Medicaid claims; and 3) the University of Colorado Health System data warehouse (Health Data Compass). Our simple, yet innovative integrated surveillance approach will utilize a combination of algorithms, incremental record linkage and targeted chart review to identify young adults with diabetes, distinguish diabetes type and estimate date of diagnosis. Our specific aims are: Aim 1: SURVEILLANCE (Prevalence)- To ascertain cases of prevalent diabetes among young adults age 18-45 years, by age, race/ethnicity and diabetes type; Aim 2: SURVEILLANCE (Incidence)- To ascertain newly diagnosed diabetes cases in young adults age 18-45 years at diagnosis, by age, race and diabetes type; Aim 3: EVALUATE PUBLIC HEALTH SURVEILLANCE METHODS - To evaluate the strengths and challenges of our integrated surveillance approach to determine the burden and incidence of diabetes among young adults 18-45 years by ascertaining validity, completeness and representativeness of case ascertainment methods.