The primary aim of this paper is to demonstrate the use of Prologmethodology to answer queries in default logics. The implementationtechniques are those of model elimination, as found in Mark Stickel’sProlog Technology Theorem Prover (PTTP). This fairly long paper is forthe most part self-contained, assuming the reader knows the fundamentalconcepts of propositional and first-order logic, and is familiar withautomated reasoning and Prolog. The paper is organized in such a waythat the theoretical underpinnings are carefully presented (with keyproofs in the appendices) and are followed by details of theimplementation and experiments in query answering.