The ongoing spread of H5N1 avian influenza in Southeast Asia has raised concern about a worldwide influenza pandemic and has made clear the need to plan in advance for such an event. The federal government has stressed the importance of planning and, in particular, has asked hospitals and public health agencies to develop plans to care for patients outside of traditional healthcare settings. These alternative or acute care centers (ACCs) would be opened when hospitals, emergency departments (EDs), and clinics are overwhelmed by an influenza pandemic. The University of Michigan Hospital System (UMHS), a large tertiary care center in southeast Michigan, has been developing a model for offsite care of patients during an influenza pandemic. This article summarizes our planning efforts and the lessons learned from 2 functional exercises over the past 3 years.