Most of the deep (systemic) fungal infections of man also occur in animals. Actinomycosis (including nocardiosis), aspergillosis, North American blastomycosis, candidiasis, coccidioidomycosis, cryptococcosis, histoplasmosis, phycomycosis (including mucormycosis), rhinosporidiosis and sporotrichosis are the principal systemic fungal infections that are common to man and animals. A listing is provided of the infections and the species of animals known to be affected. These infections are more appropriately studied with an overall view of the epidemiologic and ecologic factors involving the sources in nature and the various hosts, rather than with the restricted view that can result from the study of only one affected species. The etiologic agents often occur as saprophytes in soil or in decomposing fecal material from mammals and birds. There is little evidence of direct transmission of infection between animals and man.