African wild dogs (Lycaon pictus) are large, social canids formerly found throughout sub-Saharan Africa. Wild dogs are now endangered; only six nations hold populations larger than 100 individuals. Considerable evidence suggests that disease plays a central role in the regulation of some wild dog populations. In particular, it has been suggested that epizootics of rabies, canine distemper and anthrax can have strong local effects on wild dog numbers. Resolution of the regulatory importance of these diseases has been hampered by lack of data from wild populations. Here we report on an outbreak of anthrax among wild dogs in the Selous Game Reserve in southern Tanzania, describing clinical signs and diagnosis, measuring mortality, and testing for effects on hunting success and movements. Only one of five packs under study was affected. Immediate mortality was mild, with none of 18 adults (0%) and four of 24 pups (17%) dying. Mortality was significantly higher among puppies (<1 year old) than among adults. Mortality of individuals that showed signs of disease but did not die immediately was not significantly elevated over the following six months. The hunting success and movement patterns of the pack were not affected by the outbreak. Collectively, these data suggest that African wild dogs possess a degree of resistance to anthrax.