An unusual opportunity to study the less common pathologic changes in the tonsil has been afforded in the department of pathology of the University of Michigan through the practice of making routine histologie examinations of all tonsils received from the University Hospitals. This material now represents approximately 9,000 cases. This is a far larger series than has been reported from the standpoint of a microscopic study hitherto, and lends itself to quantitative analysis with the prospect of yielding much more accurate results, within the limitations of the data considered, than the smaller numbers forming the basis of previous studies.While tuberculosis occurs in but a small percentage of the tonsils