CDC and state and local public health authorities continue to investigate cases of bioterrorism-related anthrax. As of November 7, a total of 22 cases of anthrax have been identified according to the CDC surveillance case definition; 10 were confirmed inhalational anthrax cases and 12 cases (seven confirmed and five suspected) were cutaneous anthrax (Table 1). The majority of cases have occurred in persons working at postal facilities in New Jersey (NJ) and the District of Columbia (DC) in which letters contaminated with anthrax were handled or processed using high-speed sorting machines, or at media companies in New York City (NYC) or Florida (FL) where letters, either confirmed or presumed to be contaminated with anthrax, were opened or handled. The probable exposures for a case of cutaneous anthrax in NJ and a case of inhalational anthrax in NYC remain unknown. Epidemiologic investigations of these cases and surveillance to detect new cases of bioterrorism-associated anthrax continue. This report updates the investigation of these cases and describes adverse events associated with antimicrobial prophylaxis.