It has been widely recognised that national courts play a significant role in the process of European integration. By asking the European Court of Justice for preliminary rulings, national courts have contributed in promoting legal integration. Although previous research has recognised the importance of national courts, we still have only limited empirical knowledge on how they act. This article examines whether national courts act as promoters of legal integration or defenders of the national interest. It does so by providing a systematic investigation of: 1, what type of cases they refer to the ECJ, and 2, what type of opinions they attach with preliminary references. The article utilise data from all 67 cases referred to the ECJ during the period 1995-2009. The results indicate that Swedish courts act strategically to balance the claims of providing the ECJ with preliminary references and the demands for taking national considerations into account.