This paper discusses the relationship between the political-administrative border and the urban growth boundary around Brussels, the Belgian capital. Our hypothesis is that the interests of the various regions and language groups in Belgium interfere strongly with urban planning policies, implying that the administrative border of the Brussels-Capital Region operates in reality as an unintended urban growth boundary. Based on demographics, commuter data and property market features, we argue that this situation may cause excessive urban compaction of the Brussels-Capital Region, while spillover effects to municipalities that are rather distant from Brussels may result in undesired forms of suburbanization and long distance commuting
