During the past few years the oak wilt disease has spread with such rapidity and destructiveness among valuable forest and shade oaks in parts of the eastern half of the United States that its seriousness is now well recognized. At present oak wilt is known to be in the following states: Wisconsin, Iowa, Minnesota, Illinois, Missouri, Indiana, northern Arkansas, eastern Kansas, southeastern Nebraska, Ohio, Pennsylvania, West Virginia, northwestern Virginia, western part of North Carolina, eastern Tennessee, northeastern Kentucky, western Maryland and southern Michigan. Aerial surveys for 1952 are not yet complete, but there are indications of extensive new infections in Pennsylvania, Ohio, and West Virginia while the other states show a moderate increase in the number of infections. The first case of oak wilt in Illinois was seen in Rockford in 1942. Today 54 of the 102 counties in the state have oak wilt areas. The disease is present in both the extreme northern part and the southern-most tip of the state. Practically all wilt areas in the southern half of Illinois consist of 5 trees or less that appear to have died within the last 4 years, indicating a recent spread of the disease southward. A similar condition exists in southern Missouri and northern Arkansas. Developments in Research In 1942 a report from the Wisconsin Agricultural Experiment Station revealed that the oak wilt disease was caused by a fungus, and research programs were started early in Wisconsin and Iowa. Neighboring states were quick to follow as surveys showed a wider distribution of the disease. Now almost every state in which oak wilt occurs is taking part in efforts to learn more about the disease and its causal agent so that practical control measures may be applied before the spread of the disease gets out of hand. The National Oak Wilt Research Committee at Memphis, Tennessee, supports in part an intensive oak wilt research program in coordination with several midwestern universities and with the U.S.D.A., Bureau of Forest Pathology. Until recently the causal fungus of oak wilt was known only in its asexual or imperfect form living in the sap stream of infected trees. The most important question to be answered now is how the fungus spreads over long distances from diseased to healthy trees. Before this could be accomplished, however, we had to know how the fungus escapes from the inside to the outside of diseased trees where it can be exposed to agents of dissemination.