In this mixed-methods study, an on-line survey and interviews were utilized to gather data regarding the level of participation and expectations rehabilitation professionals have of teachers, youth with disabilities, parents, and themselves during the transition process. The survey response rate was 73.0% (N = 46). Six were selected for interviews (13.0%). Three types of rehabilitation professionals (state vocational rehabilitation counselors (counselors), community rehabilitation providers (CRPs) and centers for independent living (CIL) personnel) were involved in providing transition services; each with distinctive expectations resulting in various levels of participation and roles. Counselors report that their present level of participation is what they expect to be effective in transition services and interagency collaboration. In contrast, CRPs and CIL personnel recognize that they need to be participating more than they are now to have an effective role in transition with the exception of attending transition planning meetings. Overall, rehabilitation professionals report that the frequency of their attendance of transition planning meetings is adequate to be effective despite a large discrepancy in reported levels of participation. Both CRPs and CIL personnel expect to participate more frequently in identifying post school goals with youth and working with educators on transition issues. Likewise, CRPs and CIL personnel report wanting more communication outside of transition planning meetings with educators, youth, and parents/guardians. Further analysis provided results that suggest when rehabilitation counselors are involved in transition; they do participate at a significantly greater intensity than CRPs. Further, there is a significant difference in expectations. Counselors expect to participate at the same level as they do now while CRPs' and CIL personnel expect to participate more. These results suggest that rehabilitation counselors' participation and expectations have an impact on transition that differs from CRPs' and CILs personnel's involvement in transition services and planning. In the cases of rehabilitation counselors and CIL personnel, their roles and service provisions are mandated and supported by legislation; however, these laws are not specific to transition participation or expectations leaving room for development and implementation by individual states and local agencies. The majority of these rehabilitation professionals expect educators to initiate their participation, distribute materials, and provide leadership; with the exception of CIL personnel who view youth in this role. However, basic meeting elements such as having an agenda, ground rules, and leadership appeared lacking in most cases. These fundamentals can be manipulated to increase rehabilitation professionals' transition participation and improve their understanding of what is expected of them by educators, youth, and their parents. Rehabilitation professionals are invested in transition participation because they believe supporting youth is positive practice. Overall, the top reasons given for participating in transition activities were: (a) that transition is part of their responsibilities, (b) being invited, (c) having a transition program, and (d) having funding earmarked for transition services. While rehabilitation professionals participate in transition when they are invited and in response to referrals, they are also self-initiating their participation through outreach efforts because they believe that their contributions add value and connect youth to the community. Drawing from an intense passion for transition-age youth and wanting to assist them to reach their goals, rehabilitation professionals participate in the transition related collaboration because leadership has put policies in place that support transition practices including mechanisms for effective collaboration practices. As a supportive foundation, state vocational rehabilitation provides a critical transition role as the conduit among partners and the bridge that connects educators, parents, and youth to resources and the community. The findings of this study support the importance of further transition education and training for rehabilitation professionals. As many as a third of this study's participants reported sometimes and often not knowing what is expected of them by youth, parents, and educators. In addition, nearly a quarter of the participants reported not knowing what is expected of them during transition planning meetings. Further education specific to transition participation, collaboration, and expectations could assist in minimizing this confusion and maximize resources. While well over one-half of the study participants reported attending conferences and workshops to learn about transition; the far majority responded that their source of training was on-the-job. Therefore, it is possible that some of the transition practices being passed from one co-worker to another are based on misinformation leading to the insufficient and ineffective levels of participation and misguided expectations found in this study. Joint trainings for rehabilitation professionals and educators focused on transition are necessary. These training should include, among other information, how to: run effective planning meetings, support youth to run their own meetings, work with parents/guardians, and collaborate across systems and agencies and within communities. Additional implications for research and practice are presented. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]