Public health emergencies require rapid responses from federal, state and local authorities to prevent widespread mortality and morbidity. However, existing response plans seldom account for the variety of risks and uncertainties inherent in emergency scenarios. Our goal is to construct models that will help policy makers respond effectively to two different potential emergencies: an inhalational anthrax bioterrorist attack and an influenza pandemic. In this talk, I will give an overview of these models and show how they can help public health policy-makers evaluate and improve their emergency response plans. We will present an optimization model of the three-echelon capacitated distribution network model of the United States' antibiotic mass-dispensing system for responding to a large-scale anthrax attack; show detailed simulation models of an antibiotic-dispensing clinic and the multi-echelon supply chain that operates to support such clinics; and describe ongoing modeling efforts to help officials from the Centers for Disease Control and Prevention evaluate the possibility of using the commercial pharmaceutical supply chain to dispense antiviral medications during an influenza pandemic.