Public health officials and organizations around the world remain on high alert because of increasing concerns about the prospect of an influenza pandemic, which many experts believe to be inevitable. Moreover, recent problems with the availability and strain-specificity of vaccine for annual flu epidemics in some countries and the rise of pandemic strains of avian flu in disparate geographic regions have alarmed experts about the world's ability to prevent or contain a human pandemic. The workshop summary, The Threat of Pandemic Influenza: Are We Ready? addresses these urgent concerns. The report describes what steps the United States and other countries have taken thus far to prepare for the next outbreak of "killer flu." It also looks at gaps in readiness, including hospitals' inability to absorb a surge of patients and many nations' incapacity to monitor and detect flu outbreaks. The report points to the need for international agreements to share flu vaccine and antiviral stockpiles to ensure that the 88 percent of nations that cannot manufacture or stockpile these products have access to them. It chronicles the toll of the H5N1 strain of avian flu currently circulating among poultry in many parts of Asia, which now accounts for the culling of millions of birds and the death of at least 50 persons. And it compares the costs of preparations with the costs of illness and death that could arise during an outbreak.