This article addresses the problem of ascertaining the most suitable learning environment for learning diagnostic skills in health education--specifically diagnostic reasoning and the selection of therapy--through the design, development, and evaluation of a videodisc program. It describes the design, development, and formative evaluation of a videodisc at the University of Twente (The Netherlands) to investigate the effectiveness of two different instructional modes, expository and interrogatory. It also indicates that the hypothesis being tested in evaluating this disk, which was based on the Tennyson and Cocchiarella model for concept learning, pertains to learning outcomes of the various instances; the sequence of instances; and the effects of contrasts in the variable attributes of instances. A discussion of the theoretical background includes abstraction theory, the hypothesis approach, prototype theory, and the Tennyson and Cocchiarella instructional design model. Details are given of the design and development of three modules; the rationale for selecting the videodisc medium; recording techniques, editing, screen design, and user-interface; technical state of the art of videodisc; and compression techniques. A description of improvements that were made based on a formative evaluation of a prototype videodisc concludes the article. (Contains 24 references.) (ALF)