Although our previous studies on bacterial allergy have occupied themselves largely with the tuberculin reaction, we have, from the beginning, regarded this phenomenon merely as a specific instance of a train of occurrences probably general to all bacterial invasions of the animal body in which contact between invader and invaded exceeded the short periods of briefly acute infections, or in which—even in such brief contacts—periodic repetition occurred. Accordingly, we have from time to time published incidental experiments in which allergic reactions were observed in guinea pigs treated and tested with other bacteria (staphylococci, typhoid bacilli) (1). In pursuing these studies in greater detail, we have subjected the hemolytic streptococcus infections to a more extensive study since these organisms by their frequent invasions of the human throat would seem to represent the most important group of bacteria with which lesions or symptoms secondary to the establishment of an allergic condition might be associated.