First, a literature review was undertaken to uncover features important for designing CAI to improve learning. Concurrently, the design features and functionality of several existing CAI were reviewed. A field study of one distinctive CAI was conducted to investigate and substantiate its effectiveness. Results indicated that learners using the CAI improved their achievement significantly more than learners who did not use the CAI. Moreover, learners attributed their improved performance to using the CAI. Based on the literature review, review of existing CAI, and the results of the field study, a set of principles and a methodology for designing CAI were derived. The design principles and methodology focus the CAI design process on supporting learners' development of their mental schemas. Finally, we designed, developed and implemented a prototype web based, multimedia training system in accordance with the proposed CAI design principles. As a partial instantiation of the proposed principles and methodology, this prototype CAI provides a proof-of-concept. The design and effectiveness of the prototype CAI has been tested in a series of experiments. The corroborating evidence from these studies indicates that the prototype CAI is well-designed, usable, and an effective training tool. The demonstrated success of the prototype provides evidence of the merits of the proposed principles and methodology.