This report updates the 2004 recommendations by the Advisory Committee on Immunization Practices (ACIP) regarding the use of influenza vaccine and antiviral agents (CDC. Prevention and control of influenza: recommendations of the Advisory Committee on Immunization Practices [ACIP]. MMWR 2004;53[No. RR-6]:1-40). The 2005 recommendations include new or updated information regarding 1) vaccination of persons with conditions leading to compromise of the respiratory system; 2) vaccination of health-care workers; 3) clarification of the role of live, attenuated influenza vaccine (LAIV) in vaccine shortage situations; 4) the 2005-06 trivalent vaccine virus strains: A/California/7/2004 (H3N2)-like, A/New Caledonia/20/99 (H1N1)-like, and B/Shanghai/361/2002-like antigens (for the A/California/7/2004 [H3N2]-like antigen, manufacturers may use the antigenically equivalent A/New York/55/2004 virus, and for the B/Shanghai/361/2002-like antigen, manufacturers may use the antigenically equivalent B/Jilin/20/2003 virus or B/Jiangsu/10/2003 virus); and 5) the assessment of vaccine supply, timing of influenza vaccination, and prioritization of inactivated vaccine in shortage situations. A link to this report and other information can be accessed at http://www.cdc.gov/flu.