Expert critics have been built to critique human performance in variou
s areas such as engineering design, decision making, etc. We suggest t
hat critics can also be useful in the building and use of knowledge-ba
sed design systems (KBDSs). Knowledge engineers elicit knowledge from
domain experts and build a knowledge-based design system. The system g
enerates designs. The amount of knowledge the system possesses and the
way it applies the knowledge directly influence the performance of if
s designs. Therefore, critics are proposed to assist 1) acquiring suff
icient knowledge for constructing a desirable system, and 2) applying
proper knowledge to generating designs. Methodologies of equipping a K
BDS with critics are developed. Our practice in building and using a K
BDS shows the applicability and capability of these critics.