Because microchip technologies have changed how people have access to information, all students need to become information literate: they need to learn the search skills and strategies necessary to access, retrieve, and use information independently and astutely. Although automated high school library media programs with professional staffing have the resources to provide this instruction, student exposure to it is dependent on individual teacher discretion. If all students are to become information literate, high school principals must move this instruction into the mainstream of the school program where organizational mechanism guarantee universal student exposure.^ This multiple-site case study describes the principal roles and change implementation themes for mainstreaming instruction in one rural and one urban Connecticut high school. Site selection criteria narrowed the number of information-rich sites to three from the pool identified by chain sampling. Problems of access eliminated the only identified suburban site. Data were collected from people and artifacts and triangulated among these sources. Principal interviews were conducted using an interview guide. Library media specialists and other school personnel were interviewed using questions related to their roles and data gathered from principals. Focused coding mined the data for principal roles and implementation themes. The study\u27s trustworthiness was enhanced by triangulation of data, the positioned subject status of the investigator, detailed descriptions, peer debriefing, memoing, reflexive notes, member checks, consumer checks, and a dependability audit.^ The urban case describes the principal roles and change themes during the pre-implementation stage of mainstreaming. The study found that principals assumed roles of direction setters, facilitators, and communicators. It also found that the themes associated with successful implementation of educational change were present--vision-building, evolutionary planning, empowerment, resource mobilization, and problem-coping/monitoring.^ In the rural case, mainstreaming was accomplished by restructuring the ninth-grade program to provide the opportunity for all students to learn and practice information-finding skills. Data supported the roles of designer and communicator for the principal. The designer role encompassed visionary, architect, and transformational facilitator behaviors. Change implementation themes of vision-building, evolutionary planning, empowerment, resource mobilization, problem-coping/monitoring, and restructuring were found present.