This paper describes the Structure-Mapping Engine (SME), a cognitive simulation program for studying human analogical processing. SME is based on Gentner's Structure-Mapping theory of analogy, and provides a "tool kit" for constructing matching algorithms consistent with this theory. This flexibility enhances cognitive simulation studies by simplifying experimentation. Furthermore, SME is very efficient, making it a candidate component for machine learning systems as well. The Structure-Mapping theory is reviewed and the design of the engine described. Some examples of its operation are then demonstrated. Finally, plans for using SME in cognitive simulation studies are discussed. Appendices list detailed examples of definitions according to various analogies, as well as sample outputs. (Author/MNS)