Fogo selvagem is a form of pemphigus foliaceus indistinguishable on clinical, histologic, immunofluorescence, and ultrastructural grounds from sporadic pemphigus foliaceus found in North America and Europe. It can, however, be distinguished on epidemiologic grounds by its unique geographic distribution. The association of FS with its environment is supported by its limited areas of predilection, that is, between 500 and 800 meters altitude near rivers, and the remission of the disease when patients are removed from this environment. Owing to its obvious environmental trigger, FS may serve as a model for the initiation of autoimmune phenomena. We need merely to find the specific trigger or triggers, and the search is now under way.