Complex decision-making is a prominent aspect of requirements engineering and the need for improved decision support for requirements engineers has been identified by a number of authors. A first step toward better decision support in requirements engineering is to understand decision-makers’ complex decision situations. To gain a holistic perspective of the decision situation from a decision-makers perspective, a decision situation framework has been created. The framework evolved through a literature analysis of decision support systems and decision-making theories. The decision situation of requirements engineers has been studied at Ericsson Microwave Systems and is described in this thesis. Aspects of decision situations are decision matters, decision-making activities, and decision processes. Another aspect of decision situations is the factors that affect the decision-maker. A number of interrelated factors have been identified. Each factor consists of problems and these are related to decision-making theories. The consequences of this for requirements engineering decision support, represented as a list that consists of desirable high-level characteristics, are also discussed.