This report supplements the 2001 statement by the Advisory Committee on Immunization Practices (ACIP) (CDC. Vaccinia [smallpox] vaccine: recommendations of the Advisory Committee on Immunization Practices [ACIP], 2001. MMWR 2001;50[No. RR-10]:1--25). This supplemental report provides recommendations for using smallpox vaccine in the pre-event vaccination program in the United States.