In this contribution we present an empirical analysis of the performance of the ALCNHR+ description logic system RACE applied to TBoxes with a very large number of primitive concept definitions. Adaptions of previously known techniques as well as new optimization techniques for efficiently dealing with these kinds of knowledge bases are discussed. 1 Motivation In application projects it is often necessary to deal with TBoxes with a large number of axioms. In addition, in many applications only a small subset of the axioms are true generalized concept inclusions (GCIs). In most cases, axioms are