The paper starts with a re-iteration of the concept of appraisal of digital prototypes during the early phases of the architectural design activity and with a summary of research and development from the early seventies to the current time, the use of appraisal by progressive practices is described in the context of the company Integrated Environmental Systems. The paper then focuses as an experiment which set out to determine how the information delivered by the computer based appraisal of virtual prototypes is ordered and used by professionals in the evaluation of design alternatives. The information provided to the professionals is detailed and their self-assessment of their management and utilsation of the data is reported, together with their critique of the experience. Conclusions are drawn and future research directions proposed.