The present bulletin deals with the evolution of the school auditorium, and presents recommendations for the planning of the auditorium, with particular reference to the stage, so that the auditorium can be used as a theater, concert hall, for forums, for motion pictures, and for radio programs. The auditorium is one of the most important units in the school building and yet it is usually the least well planned. The reason for this situation lies in the fact that there is considerable confusion as to the purposes and uses of the auditorium, and this confusion as to function is naturally reflected in its plans. This bulletin aims: (1) to help clear up the confusion by showing why it exists; (2) to describe some of the tendencies toward a more organized use of the auditorium during the school day and for adults during the evening; (3) to show how the construction of the auditorium may help or seriously hinder its effective use; and (4) to submit suggestions for more efficient planning of auditoriums for school and community use. This bulletin is divided into two parts: (1) The Evolution of the Auditorium; and (2) Planning the Auditorium as a Theater. Appended are: (1) Dimensions of audience floor in 30 auditoriums in elementary-school buildings; (2) Depth of stage in auditoriums in 30 elementary-school buildings; (3) Width of proscenium arch in 30 auditoriums in 30 elementary-school buildings; and (4) Space off stage compared with width of proscenium arch. (Contains 6 figures, 11 tables, and 12 footnotes.) [Best copy available has been provided.]