We describe the 11th case of bioterrorism-related inhalational anthrax reported in the United States. The presenting clinical features of this 94-year-old woman were subtle and nondistinctive. The diagnosis was recognized because blood cultures were obtained prior to administration of antibiotics, emphasizing the importance of this diagnostic test in evaluating ill patients who have been exposed to Bacillus anthracis. The patient's clinical course was characterized by progression of respiratory insufficiency, pleural effusions and pulmonary edema, and, ultimately, death. Although her B anthracis bacteremia was rapidly sterilized after initiation of antibiotic therapy, viable B anthracis was present in postmortem mediastinal lymph node specimens. The source of exposure to B anthracis in this patient is not known. Exposure to mail that was cross-contaminated as it passed through postal facilities contaminated with B anthracis spores is one hypothesis under investigation.