BACKGROUND: Although influenza is common among children, pediatric mortality related to laboratory-confirmed influenza has not been assessed nationally. METHODS: During the 2003-2004 influenza season, we requested that state health departments report any death associated with laboratory-confirmed influenza in a U.S. resident younger than 18 years of age. Case reports, medical records, and autopsy reports were reviewed, and available influenza-virus isolates were analyzed at the Centers for Disease Control and Prevention. RESULTS: One hundred fifty-three influenza-associated deaths among children were reported by 40 state health departments. The median age of the children was three years, and 96 of them (63 percent) were younger than five ye...