BACKGROUND: Each year millions of Medicare beneficiaries in the United States receive post-acute care (PAC) in skilled nursing facilities (SNFs), inpatient rehabilitation facilities (IRFs), long-term care hospitals (LTCHs), and home health agencies (HHA). We describe, overall and by PAC setting, the national population of facilities and patients, evaluate the representativeness of a national field test sample, and describe patient characteristics in the national field test sample. METHODS: We analyzed the 2016 Provider of Service file, 2016 patient assessment data reported by PAC providers to Centers for Medicare & Medicaid, and data collected from PAC providers participating in a national field test. National data included 27,234 PAC settings and 5,033,820 beneficiaries receiving PAC. The national field test sample consisted of 143 facilities across 14 markets with 25-30 patients sampled from each facility (n = 3669). We describe PAC facility and patient characteristics for both the national and field test sample. RESULTS: Nationally, PAC facilities were more likely for-profit versus not for-profit, have an average nurse-to-bed ratio between 1:10 to 1:1 (lowest in SNFs) and be in metropolitan versus other areas. PAC patients were more likely to be white, female, and 75-89 years of age; heart failure as a primary medical condition tended to be more common than stroke or sepsis. There was limited variability across setting types. In the national field test, patients in LTCHs demonstrated a greater likelihood of cognitive impairment, positive depression screening, bowel and bladder appliance use, higher rates of medication drug classes taken, and use of therapeutic diets and IV medications. CONCLUSION: The national field test facility and patient samples were fairly representative of the national population overall and across settings with a few exceptions. Moreover, differences according to PAC setting on patient characteristics in the national field test aligned with general differences in patient populations.