The Outcome and Assessment Information Set (OASIS) is collected by the Centers for Medicare and Medicaid Services, and data is collected from all Medicare and Medicaid certified home care agencies, which comprise approximately 90% of all home care agencies. It is collected as a means to enable the rigorous and systematic measurement of patient home health care outcomes with appropriate adjustment for patient risk factors affecting those outcomes.

OASIS includes data involving the socio-demographic, environmental, support system, health status, and functional status attributes of adult Medicare and Medicaid patients. Data is available from 1999. Data is collected at the start of care, 60-day follow-ups, and discharge.