Abstract.System dynamics was originally founded as a method for modeling and simulating the behavior of industrial systems. In recent years it is increasingly employed as a Group Support System for strategic decision-making groups. The model is constructed in direct interaction with a management team, and the procedure is generally referred to as group model-building. The model can be conceptual (qualitative) or a full-blown (quantitative) computer simulation model. In this article, a case is described in which a qualitative system dynamics model was built to support strategic decision making in a Dutch government agency.Since people from different departments held strongly opposite viewpoints on the strategy, the agency had discussed its strategic problem for more than a year, but was obviously not able to reach consensus. The application of group model-building was successful in integrating opposite points of view, as well as in fostering consensus and creating commitment.The purpose of the article is twofold, first, to illustrate the process of group model-building with system dynamics; second, to evaluate why it was successful. Evaluation results reveal the importance of both systemic thinking through model-building and the role of the facilitator in catalyzing the strategic decision-making process.