Technical Abstract: Platyspora leaf spot, caused by Comoclathris pentamera (P. Karst.) S. Ahmad (= Graphyllium pentamerum (P. Karst.) M.E. Barr; = Platyspora pentamera (P. Karst.) Wehm.) was first reported as a plant disease on wheat in 1971. The fungus previously was known only at high altitudes, where it persists on the stems and leaves of numerous monocotyledonous and dicotyledonous hosts. Wheat and rye (but not barley, oats, triticale, or wheatgrass) are now known to be infected in the Great Plains of North America. At present, wheat infections are infrequent and not economically important. They appear as isolated, irregular, yellow-brown spots without internal fructifications. In the greenhouse, symptoms appear four to six days after inoculation, and infection requires 24-72 hr of continuous wetness. Natural infections eventually produce diagnostic pseudothecia on wheat straw. Ascospores (eight per ascus) are airborne, distinctly flattened, 20-30 x 10-13 x 7-9 'm, and eight-celled at maturity. Each has four transverse septa, and longitudinal septa divide the three median cells. Controls are largely unnecessary; however, those described for Stagonospora and Septoria leaf spots should also control Platyspora leaf spot.