From a review of the literature it was found that 96 species of fungi have been reported as occurring on the wood of Ulmus americana L., the Amercan elm. In an intensive study of the fungi growing on one American elm log, 60 species were found. Only one had been reported previously on American elm. A second fungus proved to be a hyperparasite of a slime mold. Three members of the Fungi Imperfecti could not be identified and is believed that they may constitute new taxa. In the past, Nasidiomycetes constituted the main group of fungi on American elm wood according to the literature. The Fungi Imperfecti were the largest group in this study in that over half of the species found are imperfect fungi. All of the species encountered in the study were illustrated.