During public health emergencies such as terrorist attacks or influenza outbreaks, the public health system’s ability to save lives could depend on dispensing medical countermeasures such as antibiotics, antiviral medications, and vaccines to a large number of people in a short amount of time. The IOM’s Forum on Medical and Public Health Preparedness for Catastrophic Events held a workshop on November 18, 2009, to provide an overview of current threats, recent progress made in the public health system for distributing and dispensing countermeasures, and remaining vulnerabilities.