The occurrence of virulent streptococci in milk and the relation of infected milk to epidemics of "septic sore throat" are now generally recognized. The object of this paper is not so much to report an epidemic of this character, which was recognized as such from a study of the cultural and other characteristics of the streptococci isolated from the patients' throats and sputum, as to detail the peculiar pathogenic powers of the streptococci from the infected milk. The epidemic occurred during February, 1914, in Elmhurst, Illinois, a city of 3,800 people. The infections, as compared with the usual epidemics of sore throat, were less severe, and the organisms isolated were of a moderate grade of virulence, being distinctly less virulent than the strains of streptococci isolated from the throats in cases of the milk-borne epidemic of sore throat occurring in Chicago in the winter of 1911-12, and studied by Capps and Miller,1 Davis,2 and Rosenow.3 In some cases, the initial infection of "sore throat" was followed by bronchopneumonia, and attacks of "rheumatic" myositis and arthritis. Investigation showed that some thirty cases had occurred in families using milk from one dairy. Dr. Langhorst, of the board of health in Elmhurst, co-operated with us in securing cultures from the cases, and the owners of the dairy supplied us with samples of milk from the various farms, eight in all. The streptococci isolated from the throats produced on blood agar plates rather large, moist colonies, surrounded by narrow, ill-defined, hazy zones of hemolysis, corresponding closely in these characteristics with the organisms isolated from the milk, and indistinguishable from the milk organisms after animal passage. The method of isolating the organisms from the milk was as follows: Seven-ounce samples of