- A scale of data-processing sophistication levels exists among users of information technology. At one end of the scale are users whose interaction with computers is minor and nondevelopmental in nature. At the other end are users who actually develop small applications. A natural result of the increase in the data-processing sophistication of users is end-user prototyping, which can either be evolutionary, leading to an operational user-developed application, or lead to a throw-away prototype, where development of the operational production system is done by professionals. Drawbacks associated with the unprofessional data-processing conduct of end-users and the lack of structure inherent in prototyping triggered this work on structured methodological support for end-user prototyping. The basis of the approach is structured prototyping, a development framework for information-systems professionals. Depending on the level of user sophistication and on system complexity, it is proposed to transfer selectively structured prototyping tasks from professionals to users. A case study is presented to demonstrate a scenario of responsibility sharing between a sophisticated user and a professional.