Influenza has been a major public health threat for centuries.  Pandemics (world-wide epidemics) of influenza have been well documented for the past four centuries, with the best-studied pandemics being those of 1918 (the Spanish Flu); 1957 (the Asian Flu) and 1968 (the Hong Kong Flu).  Substantial attention has been focused over the past year on the increasing potential for a new pandemic, in great measure because of H5N1 “avian” influenza that has spread rapidly around the world in chickens and waterfowl.  This presentation will first address influenza in historical context.  I will then briefly describe the virology and epidemiology of influenza, as well as the unique biology of influenza viruses, specifically noting how the virus escapes human immunity to produce annual epidemics as well as how the virus changes to produce pandemics.  I will briefly address the clinical manifestations associated with influenza virus infection and will relate these findings to the pathology induced by the infection.  I will close with a brief discussion of how individuals, communities, and hospitals are approaching the issue of preparedness for a possible pandemic.