Cyc is the largest existing common-sense knowledge base. Its ontology makes heavy use of higher-order logic constructs such as a context system, first class predicates, etc. Many of these higher-order constructs are believed to be key to Cyc’s ability to represent common-sense knowledge and reason with it efficiently. In this paper, we present a translation of a large part (around 90%) of the Cyc ontology into First- Order Logic. We discuss our methodology, and the tradeoffs between expressivity and efficiency in representation and reasoning. We also present the results of experiments using VAMPIRE, SPASS, and the E Theorem Prover on the firstorderized Cyc KB. Our results indicate that, while the use of higher-order logic is not essential to the representability of common-sense knowledge, it greatly improves the efficiency of reasoning.