An outbreak of foodborne hepatitis A infection compelled two regional health departments in eastern Tennessee to implement an emergency mass clinic for providing hepatitis immune serum globulin (ISG) to several thousand potentially exposed people. For the mass clinic framework, we utilized the smallpox post-event clinic plans of the Centers for Disease Control and Prevention (CDC), although the plans had only been exercised for smallpox. Following CDC's guidelines for staffing and organizing the mass clinic, we provided 5,038 doses of ISG during a total of 24 hours of clinic operation, using 3,467 personhours, or 1.45 ISG doses per person-hour - very close to the 1.58 doses per person-hour targeted in CDC's smallpox post-event clinic plans. The mass clinic showed that CDC's smallpox post-event clinic guidelines were feasible, practical, and adaptable to other mass clinic situations. ©2009 Association of Schools of Public Health.