This book is intended to be a practical reference for accessing agencies that provide transition services for students with disabilities after they exit school and for including those agencies in the transition planning process while the student is still in public school. Emphasis throughout is on interagency collaboration and the various available services. Following an overview chapter, each chapter focuses on a different agency that may provide transition support. Each chapter begins by identifying the law that mandates that agency's participation in the transition process and the agency's definition of a disability. Each chapter also includes suggested strategies for dealing with the specific agency as well as some best practices used throughout the United States. Chapters discuss the following types of agencies and programs: (1) state departments of education, (2) vocational rehabilitation, (3) the Social Security Administration, (4) mental health, (5) developmental disabilities, (6) state departments of labor, and (7) postsecondary education. The final chapter discusses interagency agreements, noting the importance of addressing agency responsibilities, referral procedures, and guidelines for accessing and exchanging tests, records, and information. Two appendices offer a sample interagency agreement and a list of national organizations and other resources. (Contains 26 references.) (DB)