Inhalation anthrax, now primarily only of historical interest, remains an intriguing disease. When the rare case occurs, it raises epidemiologic questions that are difficult to answer.

At the Second International Conference on Aerobiology in 1966,'I reported in detail on a field experiment designed to study some of the clinical and epidemiologic features of this disease. In the study we exposed 91 cynomolgus monkeys (Macaca fascicularis) to naturally occurring aerosols containing Bacillus anthracis in a goat-hair processing mill: the resultant anthrax mortality rate was 25.3%. I discussed the pathologic findings and the dose-response relationships resulting from what in effect was chronic exposure to B. anthracis. Today, I will briefly review the 18 cases of inhalation anthrax in humans that have been reported in the United States since 1900 and summarize a few of the more recent cases to point up some of the epidemiologic details of inhalation anthrax as currently seen in the United States.