This study applies a relational influence approach to analyse the European Union (EU) Nice Treaty negotiation process (2000) and explain its outcome, focusing on the influence of the Dutch cabinet in the context of the other participating actors (14 member states, the European Commission, the European Parliament and the Council Secretariat). The study attempts to answer the following research question: To what extent has the Dutch cabinet exerted its influence during the negotiation process that resulted in the Treaty of Nice, and how can this influence be explained? The method to assess and explain the influence of the Dutch cabinet consists of two parts. The first part is a before-after analysis, which involves a measurement of the extent of goal-achievement of the Dutch cabinet and the other participating actors on the Nice Treaty issues selected for this study (24 issues from the following five dossiers: Court of Auditors, European Security and Defence Policy (ESDP), Closer cooperation, Commission size and Weighting of votes in the Council). The second part of the influence analysis is a process analysis, which is divided into three steps, based on as accurate a reconstruction of the negotiation process as possible and addressing all 18 participating actors. The first step aims at assessing whether the Dutch cabinet actually exerted its influence regarding the issues on which it partially or fully achieved its goals. In doing this, the focus is on the relationship between influence attempts and goal-achievement, examining whether mechanisms other than explicit influence might account for the relationship between the two variables. The second step aims at explaining the extent of the Dutch cabinet’s influence thus found. This deductive step consists of testing the expectations of the agency and structural variables of the conceptual model. The third, inductive step considers whether yet other variables might explain the extent of the Dutch cabinet’s influence. The influence analysis is mainly based on ...