The 120 studies included in this review were grouped in relation to five categories of variables basic to a theory of instruction in patient education. Findings in the studies related to the characteristics of the patient as learner support the following variables as significant for a theory of instruction: demographic characteristics including age, race, duration and type of illness, educational level, and family preparedness. Selected psychological variables are significant as they interact with teaching approaches. Given only two studies in which the characteristics of the nurse as teacher were the main variables, no inferences for a theory of instruction could be drawn. However, the findings from those studies combined with results from studies in which characteristics of the nurse were secondary variables support the importance of this category of variables. The educational preparation, motivation, values, and job description of the nurse implementing patient teaching appear to be significant variables for a theory of instruction. Investigators explored a wide range of teaching strategies in the studies of patient teaching. The setting for teaching, group and individual teaching, and a variety of instructional strategies all prove promising at the operational level. The instructional strategies were too diverse to allow analysis at a level of abstraction beyond the operational. Findings in this review also support characteristics of the health care setting as an important category of variables for a theory of instruction. The organizational structure, a quality assurance framework, and valuing patient teaching appear to be significant variables. Patient education research provides a rich data source for future developments in theory, practice, and research. The effectiveness of patient education as a nursing intervention is clearly established. Furthermore, positive learning outcomes are associated with a broad range of teaching strategies, content areas, and patient populations. Systematic explorations of the characteristics of the patient as learner, the nurse as teacher, and the health care setting as a learning environment are still necessary for developing a theory of instruction for patient education. Future researchers should attend to phenomena unique to patient education rather than to duplicating general educational research. Instead of the investigator-driven research approach that characterizes research to date, replication should be encouraged. Future research should be designed to link theory and research and thereby contribute to the further development of a theory of instruction in patient education.