This paper reviews animal models currently in use for the study of influenza pathogenesis and immune responses to influenza virus infections and to assess vaccine and antiviral drug efficacy. Models that will be reviewed will include: models of benign influenza, typical severe seasonal influenza and pneumonia, influenza-associated sepsis, models using H5N1 viruses, models in which acute respiratory distress syndrome (ARDS) is induced, models of influenza-associated neurologic disease, models for virus transmission studies, immunocompromised models, and models of host resistance.