This paper discusses the application of computer-based instruction to the acquisition of diagnostic expertise. In the first section we outline arguments for the application of computer-based instruction to the acquisition and maintenance of diagnostic expertise. In the second we identify variables that are critical to the design of effective computer-based instruction for this purpose. In the third section we discuss and review a specific application involving acquired neurogenic communication disorders following stroke. The issues and arguments raised here apply to any form of skill where expertise depends on the mastery and use of case knowledge.