The purpose of a conceptual model is to provide an accurate reflection of the user’s requirements. However, there are many ways of formulating a universe of discourse. Although all might be argued to be equally correct, not all are necessarily equally useful. This research investigates the evaluation process of conceptual specifications developed using Unified Modeling Language (UML) conceptual models. In this paper, we primarily address the problem of assessing conceptual modeling quality. In particular, we provide a comprehensive framework for evaluating UML conceptual schemas. Furthermore, we define and examine classes of metrics facilitating the evaluation process and leading to the choice of the appropriate representation among several schemas describing the same reality. Extending quality criteria proposed in the literature, we select the subset of criteria relevant to conceptual UML schema quality evaluation and describe the implementation of this quality measurement in Rational ROSE CASE tool. For each criterion we define metrics allowing the designer to measure the schema quality. More specifically, we evaluate alternative UML conceptual schemas representing the same universe of discourse using the appropriate criteria and their associated metrics.