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. We review the Structure-Mapping theory and describe the design of the engine. Next we demonstrate some examples of its operation. Finally, we discuss our plans for using SME in cognitive simulation studies.