In this paper the application of methods and techniques from Operations Research in Purchasing Management is discussed. Traditionally, Operations Research has focused on developing models for supporting operational purchasing decisions e.g. models for determining the optimal order quantity. Despite the increasing importance and complexity of many decisions in the initial phases of the purchasing process e.g. supplier selection and make-or-buy decisions, the number of available models for supporting these decisions in an adequate manner, is surprisingly low. The significant developments however, both in Purchasing Management and in Operations Research very much justify setting up a renewed acquaintance. In this paper initial purchasing is described in terms of properties relevant to the development of formal models for decision support. Based on this description, consisting of a set of desired properties, existing models for purchasing are evaluated. Discrepancies between desired and actual properties are identified and several possibilities follow for reducing these discrepancies through the application of methods from Operations Research that so far have not been used in Purchasing Management.