The dissertation reports on a study which examined the mainstreaming practices and decisionmaking processes used in Pittsburgh Public Schools' elementary schools and investigated whether learning disabled (LD) students assigned to mainstream academic classes differed academically and behaviorally from non-mainstreamed LD students. The study was conducted in two phases: (1) selection and assessment of a sample of mainstreamed and non-mainstreamed students (grades 2, 3, and 4), and (2) an examination of mainstreaming decisionmaking processes through the use of a structured interview with school personnel. Students were administered a battery of academic and behavioral instruments and teachers reported on behavior problems. Ss were further compared with non-mainstreamed peers. Results of achievement data indicated little difference in reading scores of mainstreamed and non-mainstreamed second graders, although differences increased markedly with increased grade level. There was a large number of non-mainstreamed Ss who possessed behavioral attributes reported to be needed for mainstreaming but who were not mainstreamed. Structured interviews in phase 2 revealed that mainstreaming decisions were based on academic and behavioral strengths and weaknesses and identified patterns of participation by teachers, administrators, parents, and support staff in educational planning team meetings. Findings indicated high participation levels for special education teachers and administrators but low levels for regular educators and support personnel. (CL)