Mainstreaming is defined as the conscientious effort to place handicapped children into the least restrictive educational setting that is appropriate for their needs. The primary objective of this process is to provide these children with the most appropriate and effective educational experiences that will enable them to become self-reliant adults. This report explores: (1) how mainstreaming is operationally defined and how widespread it is; (2) the implications of mainstreaming for the responsibilities and competencies of regular classroom teachers; (3) the adequacy of teacher preparation; and (4) the efforts toward matching the preparation and responsibilities of regular classroom teachers. There are seven chapters: (1) Introduction; (2) Mainstreaming: Definition and Practice; (3) Impacts of Mainstreaming on Teachers. Roles; (4) Preparation of Teachers: Present Status; (5) Local, State, and Federal Response; (6) Discussion and Assessment; and (7) Recommendations. Included is a listing of related documents. (DMT)