A scenario is presented in which an aerosol of powdered anthrax is released, creating an invisible, odorless anthrax cloud that blows across a crowded football stadium in a large Northeastern city. The anthrax cloud infects approximately 16,000 of the 74,000 fans; another 4,000 in the business and residential districts downwind of the stadium also are infected. Two days after the game, hundreds of people in and around the Northeast become ill with fever, cough, and (in some cases) shortness of breath and chest pain. Because influenza had been seen weeks before the game, health-care providers recommended bed rest and fluids for the presumed flu. In a few days, nurses and physicians note the increased volume of serious upper respiratory illness, and some contact the city health department for treatment recommendations and a regional flu update. Patients with the earliest symptoms begin to die. The illness has been rapidly fatal, killing previously healthy young adults within 24 to 48 hours. Health department officials contact the Centers for Disease Control and Prevention (CDC). Isolation of all persons with fever, cough, or chest pain; expanded laboratory analyses; and rapid epidemiologic investigation are recommended. This isolation protocol quickly falls apart as hospital and clinic staffs struggle to cope with the surge of patients. Within 5 days of the release of anthrax, diagnostic tests support the preliminary diagnosis of anthrax. It was learned that to prevent death, antibiotics must be given before symptoms occur or in the earliest hours after symptoms begin. Of the 20,000 persons originally infected, 4,000 died, most in the first ten days after the attack. The media report that hundreds, if not thousands, needlessly died because of delays in antibiotic distribution. Practical, modest preparedness efforts could make a difference and change the outcome of this scenario.