Implications of using authentic activity as a model for appropriate learning activity are discussed, particularly in regard to the design of computer-based simulations and project-based learning activities. Mere provision of computer-based simulations and reality-centered projects does not ensure that a student will derive the benefits of in-context learning. Characteristics of real-life problem-solving tasks, such as ill-structured problems, complexity, and duration, must be incorporated. The cognitive apprenticeship framework provides the primary rationale for using authentic activity as a model for appropriate learning activities. Theory suggests that learning outcomes are maximized when fidelity and complexity are added progressively in the simulation. A useful way to regard authentic learning activity is to see it as a simulation in which instructional overlay is designed to support a related set of values, integrating ends with means. Design must support the learner in establishing a learning enterprise within the global task environment, and the learning situation must afford activities that can be transferred to the real environment. (Contains 29 references.) (SLD)