This report updates 1999 recommendations by the Advisory Committee on Immunization Practices (ACIP) on the use of influenza vaccine and antiviral agents (MMWR 1999;48[No. RR-4]: 1-29). These recommendations include five principal changes: a) the age for universal vaccination has been lowered to 50 years from 65 years; b) scheduling of large, organized vaccination campaigns after mid-October may be considered because the availability of vaccine in any location cannot be assured consistently in the early fall; c) 2000-2001 trivalent vaccine virus strains are A/Moscow/10/99 (H3N2)-like, A/New Caledonia/20/99 (H1N1)-like, and B/Beijing/184/93-like strains; d) information on neuraminidase-inhibitor antiviral drugs has been added; and e) a list of other influenza-related infection control documents for special populations has been added. This report and other information on influenza can be accessed at the website for the Influenza Branch, Division of Viral and Rickettsial Diseases, National Center for Infectious Diseases, CDC at <http://www. cdc.gov/ncidod/diseases/flu/fluvirus.htm>.