In November, 1929, and again in May, 1931, Schick and one of us (Dr. Topper)1 reported the results of studies of the effect of tonsillectomy on immunity to diphtheria. Of 151 children who had shown a positive reaction to the Schick test before tonsillectomy, 123 (81.5 per cent) showed a negative reaction six months after tonsillectomy, while 28 (18.5 per cent) still gave a positive reaction. As the number of children whose reaction would normally become negative during this period is about from 10 to 15 per cent, it was concluded that tonsillectomy had in some way favored the development of a humoral immunity against diphtheria as measured by the Schick reaction.
Since the publication of these reports, we have continued the study. In this paper, we report the results in 81 children who gave positive reactions before tonsillectomy and who returned for retesting six months later. All of