In learning environments which provide little structure (e.g., hypermedia systems) students have an especially strong need to regulate and control their own learning. However, a review of the literature indicates that merely providing learners with flexible learning environments does not necessarily mean that they will effectively explore and learn meaningfully from the resources provided. It has been suggested from previous research that poor metacognitive skills, that is the inability to accurately monitor, reflect, evaluate, and adjust learning, hinders learning in this free environment. Metacognitive theory and research are reviewed, and recommendations are made for future research in hypermedia-based instruction and learning. (Contains 71 references.) (Author/JLB)