OBJECTIVE. Pediatric influenza-associated death became a nationally notifiable condition in the United States during 2004. We describe influenza-associated pediatric mortality from 2004 to 2007, including an increase of Staphylococcus aureus coinfections. METHODS. Influenza-associated pediatric death is defined as a death of a child who is younger than 18 years and has laboratory-confirmed influenza. State and local health departments report to the Centers for Disease Control and Prevention demographic, clinical, and laboratory data on influenza-associated pediatric deaths. RESULTS. During the 2004–2007 influenza seasons, 166 influenza-associated pediatric deaths were reported (n = 47, 46, and 73, respectively). Median age of the children was 5 years. Children often progressed rapidly to death; 45% died within 72 hours of onset, including 43% who died at home or in an emergency department. Of 90 children who were recommended for influenza vaccination, only 5 (6%) were fully vaccinated. Reports of bacterial coinfection increased substantially from 2004–2005 to 2006–2007 (6%, 15%, and 34%, respectively). S aureus was isolated from a sterile site or endotracheal tube culture in 1 case in 2004–2005, 3 cases in 2005–2006, and 22 cases in 2006–2007; 64% were methicillin-resistant S aureus. Children with S aureus coinfection were significantly older and more likely to have pneumonia and acute respiratory distress syndrome than those who were not coinfected. CONCLUSIONS. Influenza-associated pediatric mortality is rare, but the proportion of S aureus coinfection identified increased fivefold over the past 3 seasons. Research is needed to identify risk factors for influenza coinfection with invasive bacteria and to determine the impact of influenza vaccination and antiviral agents in preventing pediatric mortality.