Avian cholera is reported for the first time in Canada geese, Branta canadensis, of the Mississippi Valley population. The disease was detected in weekly surveillance transects and was responsible to the loss of about 850 geese during the winter of 1978–1979 at localized areas in southern Illinois. Necropsies performed on 480 geese that died at Union County Conservation Area and on 133 birds at Horseshoe Lake Conservation Area during January and February 1979 revealed that the majority of losses (649%) were caused by avian cholera. Lead poisoning was responsible for the death of 14% of the geese analyzed and the remaining 22%, most of which were decomposed, were undiagnosed. Lethal lead levels and Pasteurella multocida occurred concomitantly in a few instances.