This is an introduction to seven papers reporting the results of arbovirus studies conducted in the central Ohio-Mississippi Basin from 1964 through 1967. Several arboviruses were isolated, but the focus was on St. Louis encephalitis virus. Evidence of disease in human population groups was procured through liaison with practicing physicians and official health agencies. Mosquitoes and birds were collected, as well as limited numbers of ectoparasites and small mammals. Suckling white Swiss mice were used in all attempts to isolate virus. Subsequent identification of isolates was usually based upon results of complement-fixation and neutralization tests. The latter technique (NT) and the hemagglutination tests were used in serologic surveys.