The constituting elements of distance education are the course and the interaction between students and supporting organizations. Compared with students at traditional universities, distance students are generally older, have jobs, and often have families. In distance education, learners are usually isolated and want to broaden their education, not receive a degree. Many distance education courses are characterized by a high level of structuring; they provide few incentives for the development of an active-constructive conception and rather lead to a passive-reproductive conception. Distance learning demands a high degree of self-discipline, organization, and planning. Studies have demonstrated that all teaching and learning theories can be easily applied to distance education. The most important medium is still written material. Theories of text comprehension include additive-elementary, holistic, and integrative approaches. No instructional theory makes it possible to coordinate the implications of these theoretical approaches into instructional rules manageable for practical use. Aids to a learner-friendly text design are readability formulas and concepts for the assessment of the text comprehensibly and general evaluation procedures. Learning aids can include advance organizers, learning objectives, and questions in the text. The possibilities of telecommunication to decrease the turnaround time are important because long turnaround times hinder motivation and increase the dropout rate. (Contains 229 references.) (YLB)