An overview is provided of the principles of cognitive psychology that can be used to enhance the effectiveness of computer-assisted instruction (CAI). First, the paper looks at the features of classical and operant conditioning that provide the foundation for important parts of mastery learning and CAI programs. Next, findings from four areas of cognitive psychology research and theory are discussed in terms of their applicability to CAI: (1) modern knowledge about how people learn concepts, retrieve them from memory, learn to discriminate among similar concepts, and apply their knowledge of a concept to unfamiliar situations; (2) human limits in memory, attention, and mental processing; (3) the role of goals and performance standards in cognitive processing; and (4) principles of remembering and forgetting that stress the importance of relevance, organization and integration, elaborated processing, the match between conditions at learning and conditions at retrieval, and memory erosion and interference. Within each section, and in a separate summary, research-based suggestions for CAI development and practice are presented (e.g., when teaching concepts, present a set of positive examples covering the range of instances that fit the concept to help students generalize new examples, and present a set of negative examples to help students discriminate among superficially similar concepts; provide the student with control over the program; define ultimate and short-term instructional goals; and provide edit and correct practice). (EJV)