This book, which is intended for distance educators and students of the theoretical foundations of distance education, offers a conceptual model of distance education and recommendations for policy and practice that link the principles of instructional design and the provision of learner support. Discussed in the first four chapters are the following topics: adult students in open and distance learning courses, student progress and dropping out, theories of persistence, and development of a theory for open learning. The next six chapters, which all illustrate and explain the model, examine the following topics: development of a model of open learning, entry characteristics of students, social integration, external attribution, factors determining academic integration versus incompatibility, and factors associated with course completion and dropping out. Chapters 11 and 12 present the results of initial quantitative and replication tests of the full model on samples of students from three courses. The remaining four chapters focus on the model's implications for policy and practice, with special attention to the following: integration through instructional design, academic integration through tutorial support, counseling for social integration, and future directions. Appended are an interview schedule and distance education student progress inventory. (Contains 32 tables/figures and 274 references. (MN)