Summary1) No satisfactory method of. treatment of diphtheria carriers by disinfectants has yet been reported.2) When the diphtheria bacilli persist in the throat, they will be found in the tonsils, which then usually present pathological alteration of various kinds. Of the methods of treatment recommended, tonsillectomy appears to be the most effective in such cases. The author discusses the indications and gives his views. In 9 cases of his own, the author tested this type, of treatment and had good results in them all. No complications occurred after operation, whether prophylactic diphtheria serum had been administered or not, but it is advisable to give such prophylaxis even when the patient has previously been given serum at the time of the appearance of the clinical symptoms.3) Concerning the technique, complete extirpation of the tonsils should be striven for, since it has been found that even insignificant tonsillar remnants rich in recesses may maintain the diphtheria bacilli after operation.4) When the bacilli persist in the nose, local pathological conditions of various kinds appear to predispose to the maintenance of the bacilli. The author is inclined in most cases to regard persistence of the diphtheria bacilli in the nose as a criterion of the presence of some complications or anatomical defect (foreign bodies).5) In 6 such cases, the author has proceeded on the principle that the patho‐anatomical condition as such should be treated without regard to the presence or absence of diphtheria bacilli, and without any specific disinfection against them. In all his cases, the bacilli have, as a matter of fact, disappeared (whetherpostorpropter, it is impossible to say) simultaneously with the objective disappearance of the pathological processes, in one case after the extraction of a foreign body, in 4 after drainage in sinusitis, and in one of atrophied rhinitis after simple hygienic measures, such as flushing with physiological salt solution.6) Treatment along these lines, to be efficacious, may not be given according to set rules, but individually, and based on a painstaking diagnosis, after careful consideration.7) The results do not furnish ideal proof, but careful clinical observation strengthened the author in his opinion as to the correctness of these principles of treatment.8) A sufficient number of negative testsafter termination of the treatmentis required. The author has endeavoured to obtain 10 or more, and in several cases, subsequent control tests were made.9) The question of a positive virulence test as a prerequisite for active therapy has been mentioned, but not dealt with at length, since it lies beyond the scope of this paper, the object of which has been to demonstrate the possibility in most cases of attaining complete freedom from bacilli within a resonable length of time by means of active therapy along the lines mentioned herei