One of the arguments for choosing description logics as the basis for the Web Ontology Language is the ability to support the development of complex ontologies through logical reasoning. Recently, significant work has been done on developing advanced methods for debugging erroneous ontologies that go beyond the pure identification of inconsistencies. While the theory of these methods has been studied extensively little attention has been paid to the application of these Methods in practice. In this paper, we evaluate existing implementations of advanced methods for debugging description logic ontologies. We show that most existing systems suffer from serious problems with respect to scalability but surprisingly enough also with respect to the correctness of the results on certain test sets. We conclude that there is a need for further improvements of existing systems in particular with respect to bridging the existing gap between theory and practice of debugging ontologies.