This report updates the 2008 recommendations by CDC's Advisory Committee on Immunization Practices (ACIP) regarding the use of influenza vaccine for the prevention and control of seasonal influenza (CDC. Prevention and control of influenza: recommendations of the Advisory Committee on Immunization Practices [ACIP]. MMWR 2008;57[No. RR-7]). Information on vaccination issues related to the recently identified novel influenza A H1N1 virus will be published later in 2009. The 2009 seasonal influenza recommendations include new and updated information. Highlights of the 2009 recommendations include 1) a recommendation that annual vaccination be administered to all children aged 6 months-18 years for the 2009-10 influenza season; 2) a recommendation that vaccines containing the 2009-10 trivalent vaccine virus strains A/Brisbane/59/2007 (H1N1)-like, A/Brisbane/10/2007 (H3N2)-like, and B/Brisbane/60/2008-like antigens be used; and 3) a notice that recommendations for influenza diagnosis and antiviral use will be published before the start of the 2009-10 influenza season. Vaccination efforts should begin as soon as vaccine is available and continue through the influenza season. Approximately 83% of the United States population is specifically recommended for annual vaccination against seasonal influenza; however, <40% of the U.S. population received the 2008-09 influenza vaccine. These recommendations also include a summary of safety data for U.S. licensed influenza vaccines. These recommendations and other information are available at CDC's influenza website (http://www.cdc.gov/flu); any updates or supplements that might be required during the 2009-10 influenza season also can be found at this website. Vaccination and health-care providers should be alert to announcements of recommendation updates and should check the CDC influenza website periodically for additional information.