In studies on political decision-making, attention is often limited to domestic factors. However, this study demonstrates that international considerations can play a key role in the decision-making process. Since 1980, competence for environmental policy in Belgium is shared by the national government and the three autonomous regions. The 134 most important environmental measures which have been issued in Flanders since 1980, were studied, and international influence proved to be considerable. In 78 cases, the measure was brought into being due to the environmental policy of the European Community. In 39 cases, there were influences from other sources of international environmental policy. This left only 17 measures which had no clear connection with international environmental policy. It seems that policy scholars have not yet fully realized the extent of this shift of power from the national to the international level, and have rather neglected the international decision-making process.