The paper is a product of the 3-year project, "Functional Mainstreaming for Success," designed to develop a model for instructional mainstreaming of handicapped children (3-6 years old) in community settings. The model was implemented with three mainstreamed preschool classrooms in which half the children were handicapped. Large group, small group, and a minimal amount of one-to-one instruction is used as is increased structure within the curriculum. The rationale for emphasizing group rather than the traditional individual curriculum in a combined comprehensive delivery system is discussed. Guidelines for developing effective groups include assessing all children, establishing individualized education programs for handicapped students, developing a core curriculum, planning integrated groups, and structuring one-to-one sessions. Preliminary evaluation results indicated handicapped children participated significantly in mainstream activities while achieving at the same or better levels than they did in earlier self-contained classes. Parent and staff reactions to the reverse mainstreaming program were positive. (DB)