The Examining Relationships in an Integrated Hospital System research project with RTI explores whether an organizational link between a Medicare hospital and a Medicare post-acute care (PAC) setting, such as a long term care hospital, inpatient rehabilitation facility, skilled nursing facility, or home health agency, increases the likelihood of transfer to a Medicare PAC setting. RTI uses calendar year 2005 data to build patient-level episodes beginning with an acute hospital discharge and tracking patient transfer patterns across settings. The project provides information on the national distribution of Medicare acute and PAC providers and their organizational relationships, both formal and informal. The organizational relationships are defined as freestanding PAC providers, provider-based PAC, or co-located providers (i.e., those within 250 yards of other providers). The initial findings include multivariate analysis of the effects of these organizational relationships on PAC site of care choices.