Two types of intelligent measurement systems are considered: commercially produced instrumentation systems with intelligence incorporated as a part of the product and instrumentation systems developed in-house in which the intelligence resides in stand-alone microcomputers linked by an appropriate machine level interface. The system evaluated is an example of the latter type, but the comments are equally relevant to the former. Evaluation is considered as a mainstream activity and illustrated by reference to an intelligent management system for patients who require ventilatory therapy. It is carried out for small functional units individually becoming a more transparent activity. Its more explicit nature has aided system designers and system users to view potential problems from the same perspective. >