Context: The COVID pandemic has renewed attention on social isolation and loneliness among older adults, while also rapidly accelerating the use of telehealth. It is unclear how social isolation and loneliness, which have previously been linked with poor health outcomes, may be associated with telehealth use. Objective: To assess the rates of telehealth use in a Medicare population and explore possible determinants of telehealth use, including social isolation and loneliness. Study Design: Secondary analysis of the National Health and Aging Trends Study (NHATS) and COVID supplement. NHATS is an annual survey of a nationally representative sample of Medicare enrollees. The COVID supplement was collected as a mail survey of NHATS participants from June 2020 to January 2021, with data released in July 2021. Setting: United States. Population Studied: 3257 Medicare beneficiaries aged 65 years and older completed both Round 10 of NHATS and the COVID supplement. Main and Secondary Outcome Measures: Rates of telehealth use, social isolation (based on a previously validated NHATS measure), and loneliness. Health assessments, additional indicators for social isolation, technology use, and demographics will also be assessed. Results: 23% of respondents reported learning new technology during COVID. Respondents self-reported increase in the use of both video visits and phone for communication with their usual health care provider during the pandemic compared to pre-pandemic while reporting a decline in in-person visits. The reported use of video visits increased from 4% to 19%, phone increased from 48% to 61%, and in person visits declined from 87% to 57%. Analyses are ongoing to test the association between patient factors and telehealth use. Telehealth use could be either higher or lower among socially isolated individuals, depending on whether use is a protective strategy to mitigate isolation and loneliness or if isolation and loneliness are a cause for less telehealth use. We hypothesize greater use among participants with caregiver/helper support and greater baseline technology usage. Conclusions: The rapid expansion of telehealth use in older adults during COVID calls for better understanding of the characteristics of persons who have lower usage of telehealth. This in turn will allow for tailored interventions to support healthcare access and improve outcomes.