Discusses the utility of instructional design principles for optimizing adaptation in open learning environments. The 1st section elaborates basic concepts from instructional psychology pertaining to self-regulated, goal-directed learning. Postulated teaching functions related to learner motivation and learner control are outlined, as are those related to the processing, storage, application, and transfer of information. Adaptive learning emerges when the responsibility for the regulation of these teaching functions is distributed dynamically between learner and learning environment. Reporting experimental findings involving computer-based instruction, 10 adaptation principles are differentiated that have proven to facilitate learning. These adaptation principles refer to the systematic variation of: instruction load, the sequence of instructional units, information content, presentation format, task difficulty, concept definitions, system response time, the advice in exploratory learning environments, the menu structure of computer-based training programs, and the balance between system and learner control. The last section provides suggestions for applying the 10 principles to open learning environments.