Abstract Endemic pemphigus foliaceus is an autoimmune disease that has remarkable features. Endemic foci are found in characteristic environments within the interior of Brazil. The epidemiologic data strongly suggest that an environmental factor initiates the autoantibody response in the host. As such it is an important disease for in-depth study. A group of interested investigators in both Brazil and the United States has been formed to attempt to do just that. As part of the overall effort, this Cooperative Research Group for the Study of Fogo Selvagem presents a definition of the disease, a proposed clinical classification for various forms of the disease, and an outline of what is currently known of its immunopathologic characteristics.