In most cases, influenza is not fatal, even without treatment. Moreover, vaccination and antivirals have reduced influenza-related mortality in recent years. However, the direct transmission of avian influenza viruses to humans with lethal outcomes in Hong Kong in 1997 was a potent reminder of the devastating potential of the disease. Currently, H5N1 avian influenza viruses are circulating in many Asian countries, and the human death toll continues to rise as the virus spreads to European countries as well. Since the beginning of the outbreak in Asia, more than 120 cases have been confirmed and the mortality rate has been no less than 50%. Current vaccines for H3N2 and H1N1 viruses, of course, have no effect on infection by H5N1 viruses. In addition, H5N1 viruses that are resistant to the antiviral drugs amantadine and oseltamivir have emerged. Fortunately, a virus that is capable of efficient transmission among humans has not emerged. However, it is not a matter of if, but when, such a virus will appear. Here, we review the current situation of avian influenza and pandemic preparedness.