In this paper the C-CLASSIC Description Logic is used to design the retrieval and selection tasks of a Case-Based Reasoning system with homogeneous, explicit and formal criteria. The case base is organized by means of a taxonomy of index concepts. Case retrieval is performed using the automatic concept classi cation of the description logic. Case selection is performed using two criteria: similarity and dissimilarity. Similarity between two cases is characterized by the most speci c concept which subsumes the two cases (Least Common Subsumer or LCS), and dissimilarity by a concept representing properties which belong to one case but not to the other. A partial order induced by the subsumption relationship on these concepts is used to select the most similar cases.