Within the last decade the activity period has been adopted by an increasing number of high schools, even in those unaffected by bus transportation schedules. These schools believe it is a means for developing desirable civic and social activities for "all" pupils and for applying the "total" resources of school staff and equipment to the pupil activity program. They contend that activities serving the needs of only a segment of the student body and sponsored by only a part of the faculty are only half-way programs. Half-way programs convince neither pupils nor teachers of the importance of their joint responsibility for integrating activities with the formal school program. The purpose of this publication is to report practices regarding activity period organization in public high schools. The hope is that this data, obtained from the replies of 10,925 public high schools to the Inventory of Offerings and Enrollments in High-School Subjects, will be helpful to the profession generally and will stimulate further inquiry into the problem of how best to organize effective pupil activity programs in meeting the needs and interests of all secondary school youth. It was found that most high schools adopt one of three patterns in organizing extraclass activities: (1) The activity period, which is intended to provide for most extraclass activities "within" the daily time schedule; (2) The core program, which consolidates many of the extraclass activities with the class activities; and (3) The before-school and after-school activities program, which provides for most of the extraclass activities "outside" of the regular school session. (Contains 4 tables and 12 footnotes.) [Statistical tables in this bulletin were prepared by Robert C. Story. Best copy available has been provided.]