For many years irradiation has proved to be of considerable benefit in cases of hyperplasia of the lymphoid tissue in the nasopharynx. What are the actual results of treatment in clinical practice? What is the most effective method of irradiation? In an attempt to answer these questions we have reviewed our results in several hundred cases and have summarized the relative physical effectiveness of the two commonly applied methods of irradiation. ANATOMIC CONSIDERATIONS In adults the eustachian tubes are about 3.6 cm. in length and the orifices usually 4 cm. apart. The bony portion of the eustachian tube comprises the outer third; it joins the cartilaginous portion at the isthmus, or narrowest part of the tube. The size of the tube increases as it reaches its pharyngeal end. Normally the walls in its mesial half are apposed; its ostium is vertical and slitlike except when forced open by muscular action