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. Thirty-two sources were reviewed which deal with the teacher competencies needed by regular teachers for successful mainstreaming. Sources include pragmatic summaries of personal experiences, comparison of teachers' and professors' views on teacher competencies, a dissertation based on teachers' reports of successful and unsuccessful mainstreaming experiences, competencies judged essential for teacher certification, and a review of Deans' Grant Projects. Twenty major competency areas were identified by at least one-fourth of the sources as essential. Three additional competency areas mandated by the long term needs of handicapped students are also identified. The 23 competencies are outlined and include: prepare class for mainstreaming, assess needs and set goals, evaluate learning, understand curriculum, conduct effective parent-teacher relationships, teach fundamental skills, understand exceptional conditions, conduct professional consultations, understand the nature of mainstreaming, foster student-student relationships, be aware of attitudes, be knowledgeable about resource and support systems, manage the learning environment, demonstrate competent interpersonal communication, teach communication skills, supervise aides and volunteers, individualize teaching, manage the class, use appropriate teaching techniques, understand legal issues, carry out behavior modification appropriately, be able to analyze tasks, and teach social skills. (DB)