Selecting the optimum prefabricated post-and-core system can be a complex and imprecise exercise for the restorative dentist. First, no single prefabricated post-and-core system fits all situations. Second, the vast number of post-and-core components currently on the market complicates the selection process. Finally, useful biomechanical criteria for evaluating prefabricated post-and-core components are difficutl to quantify. The prefabricated post-and-core system consists of three components: the post, a core material, and a luting cement. Each combination of component types is a potential system alternative. This article presents useful biomechanical criteria, based on current restorative guidelines, for evaluating the basic components of any prefabricated post-and-core system.