A three phase study was conducted on the role of regular classroom teachers in implementing individualized education programs (IEPs) for mainstreamed special education students. IEPs in 20 elementary sites were reviewed in phase 1, 59 elementary teachers were surveyed in phase 2, and 16 of those surveyed participated in interviews in phase 3. Five major research issues were addressed in the study: role specification of the IEP document, characteristics of the IEP implementer, environmental characteristics, and child characteristics. Findings from the three data sources were highly consistent, suggesting that regular class teachers were basically uninvolved in the formal aspects of IEP development and implementation (they typically did not attend IEP meetings, did not receive a personal copy of the completed IEP, and rarely referred to one when they did have it). Teachers with more skills, training, and experience in special education, and those who had students from resource specialist programs, were likely to be more involved in the formal IEP process. Informal involvement in the process was noted through meetings with special education teachers. It was concluded that regular class teachers should be included in IEP meetings whenever possible, should be provided with a personal copy of the IEP, and should be given training in diagnostic/prescriptive teaching, special education techniques, collaboration skills, available special education services, and relevant legislative requirements. (CL)