While measures such as closing schools and social distancing may slow the effects of pandemic influenza, only vaccines and antiviral drugs are clearly efficacious in preventing infection or treating illness. Unless the pandemic strain closely resembles one already recognized, vaccine will not be available early. However, studies can be conducted beforehand to address questions concerning vaccine dose, frequency of inoculation, and need for adjuvants. In contrast, antiviral drugs, particularly the neuraminidase inhibitors, will be effective for treatment and available if stockpiling takes place. Special questions need to be answered if a highly lethal virus, such as influenza A (H5N1), produces the pandemic. Both vaccines and antiviral drugs will be required for a coordinated strategy.