This paper describes our current activities to supply extended reasoning support to knowledge engineers who are building terminologies using Description Logics (DL) reasoners. The new services originate in the development of the DICE1 terminology where the lack of appropriate debugging or explanation facilities hindered a more efficient (and possibly more concise) construction of a corresponding DL TBox. We discuss a number of alternative methods to explain incoherence of TBoxes, unsatisfiability of concepts and concept subsumption.