In this chapter we focus on the early stage of evaluating and selecting an ERP system prior to implementation. Only a part of decision making for ERP systems can be handled by a definite or accepted procedure such as standard investment calculations. There are many other intangible decision-making criteria needing to be judged and evaluated by the decision makers. There is no agreed-upon and formal procedure for this important task (Hecht 1997; Laudon & Laudon, 1998). Therefore it seems necessary to investigate decision-making practices to increase the understanding of this complex and important task. We also focus on the decision-making situation faced by small and medium-sized enterprises (SMEs). This is of particular importance because SMEs are more and more experiencing the need for integration, especially for interorganizational integration, and expecting ERP software to fulfill these needs. The availability of relatively inexpensive hardware is fostering this situation (Gable & Stewart, 1999). In general, decision making in SMEs features much greater constraints on the ability to gather information in order to reduce uncertainty about their investment (Cobham, 2000). Considering ERP software decisions with its complex and far-reaching implications, poor decision making by SMEs can result in disastrous situations.