Our ability to create effective user interfaces for products has fallen behind the power and complexity of devices now being produced. Aspects of the user interface which act upon the kinesthetic sense, through physical contact and the consequent power transfer between operator and device, are often specified without recourse to methodology. However, such aspects may be crucial to the entire interface's intuitiveness and ease-of-use. In the absence of a systematic means of prototyping and testing kinesthetic interface characteristics, product designers must rely instead on intuition and experience with similar design problems. A first-generation kinesthetic prototyping tool is being developed which will use a high bandwidth DC motor to generate force-position profiles of input controls such as linear potentiometers, slider switches and buttons. The kinesthetic simulation will be augmented with real-time computer-graphic images of the device being acted upon and the larger interface context in which it resides. On completion of the system, human subjects will be tested to ascertain the actuation and graphical performance specifications required to create an illusion sufficiently convincing to be useful for kinesthetic prototype evaluation. Future generations of simulation devices will be designed and built to expand upon the generality of design problems addressable with this approach.