The data comprising this report were accumulated during the period 1930 to 1935 inclusive. The observations include (1) bacteriologic and serologic studies in the Iowa State Hygienic Laboratories; (2) special reports on 705 cases submitted by attending physicians to the Division of Communicable Diseases and Epidemiology, Iowa State Department of Health; (3) personal observations and detailed records of cases presenting unusual clinical features, chiefly patients admitted to the State University Hospitals, and (4) comparative data collected from the different states through the office of the director of the National Institute of Health, Washington, D. C. Certain observations in our reported series of 375 cases for the period 1927 to 1929 are also considered. Supplementary information was also drawn from the current literature. ETIOLOGY The various strains of Brucella isolated from patients in Iowa for the nine years 1927 to 1935 numbered 127 (table 1). All but ten of the organisms