The construction of a decision support system must define its information requirements. Building an expert system needs knowledge acquisition - the accumulation, transfer, and transformation of problem-solving expertise from some knowledge source. There are a few methods associated with the information requirement elicitation (IRE) and knowledge acquisition (KA). This paper compares representative IRE and KA methods. It concludes that though most methods can be applied to both types of systems, there are still few methods that are unique to one type.