In order to evolve more efficient means of treatment, it is necessary to review, periodically, various cases and compare results with those in the literature. We have therefore prepared a review of all malignant lesions of the faucial tonsil treated in the Department of Deep X-ray Therapy of the University of Minnesota Hospitals during the period 1926 through 1950. This group comprises 103 cases in all. Two cases have been eliminated because they were treated elsewhere before being seen here. We have, then, 101 cases to examine. Histologically, these fall into the following groups: This distribution agrees satisfactorily with other series reported but is at variance with the opinion of Smith and Gault (13) that the transitional-cell carcinoma is the most frequent lesion of the tonsil. Pathologically, malignant lesions of the tonsil can be separated both grossly and microscopically. Grossly, the carcinomas are usually exophytic and frequently arise from the upper pole, spreading to the soft palate. They often ulcerate and form infiltrative lesions with hard rolled edges. Microscopically, they can be divided into three groups. The squamous-cell carcinomas (Fig. 1), are characterized by nests and cords of squamous cells invading normal tissues. They may show varying degrees of keratinization and epithelial pearl formation. Mitotic figures are not prominent ordinarily. The transitional-cell carcinoma (Fig. 2) is made up of cells of relatively uniform size, with clear cytoplasm and oval hyperchromatic nuclei. Mitotic figures vary greatly in number, and keratinization or epithelial pearl formation is not seen. The tumor tends to grow in solid sheets and invades widely. The undifferentiated carcinoma is a microscopically indeterminant form which can be classified neither as a squamous-cell carcinoma nor as a true transitional-cell carcinoma. It is usually of a high grade malignancy. Of less frequent occurrence is the lymphoepithelioma, which is felt by many to be a carcinoma of either the transitional or undifferentiated type. This lesion makes up 4 to 8 per cent of the total group (2). However, because of its different clinical behavior, it is often considered as a separate lesion. As described by Regaud, it is characterized by cords of clear epithelial cells infiltrated by numerous lymphocytes (Fig. 3). It metastasizes to lungs, liver, and bones, and carries to the metastases its distinctive histologic pattern. Grossly the tumors are smooth and sometimes lobulated. The cervical lymph nodes are almost always involved. The lymphoepitheliomas frequently ulcerate after attaining a large size, and metastasize rapidly and widely. The lymphosarcomas ordinarily do not ulcerate but become very large and frequently produce symptoms of obstruction. There is often bilateral cervical lymph-node involvement. The tonsil may be the original site of disease, with rapid generalization, but at least one series shows a high incidence of five-year survivals (7).