Background/Aims: For seniors with multiple chronic conditions, patient-reported outcomes (PROs) can provide meaningful information on patients' health, well-being and effects of treatment that transcend specific conditions. Effective use of PROs for clinical care and research requires an understanding of their availability and accessibility. Methods: The data and measures workgroup of the HCSRN-OAIC Advancing Geriatric Infrastructure and Network Growth (AGING) Initiative conducted an electronic survey to inventory PROs available at each HCSRN site and to understand their storage and accessibility. PRO domains inventoried included: self-rated health, functional status, mood, pain, cognition, fall risk and advance directives. For each domain, sites were asked to list specific measures used and to describe PRO data collection, storage and extraction. The inventory was distributed through the HCSRN governing board to representatives at each site. Results: To date, 15 of 19 HCSRN sites have fully or partially completed the inventory. Four were unable to participate due to lack of PRO data or resources. The majority of sites rely on a combination of systematic outreach and patient initiation to complete the annual wellness visit (AWV) questionnaire, with the most complete data coming from the past 5 years. The percentage of Medicare patients completing an AWV questionnaire varies among sites, ranging from 5% to 43%. The most common method of storage is via "Smart Text" within text fields of the electronic health record. For the AWV, most sites address three or more of the PRO domains included in the inventory and many address additional domains as part of the AWV such as oral health, diet, exercise, incontinence, substance use and social needs. Conclusion: Although there is some overlap, the method of collection, storage and availability of PROs gathered as part of the Medicare AWV vary widely across HCSRN sites. While there has been an improvement in the availability of this information in recent years, most sites' AWV questionnaire coverage remains low. The final inventory results will inform data infrastructure development and data collection processes across the HCSRN, and will facilitate engagement in multisite aging research related to multiple chronic conditions.