The current debate on polycentric urban development suggests that inter-firm relations are important for the creation and sustainment of urban networks. Conceptually, the degrees of spatial and functional integration and urban complementarities in economic network relations are hypothesised to be important. However, the theoretical economic rationale has not been convincingly tested. In this paper, we use data on inter-firm relations in the Dutch Randstad to test conditions for integration and the existence of economic complementarities within this region. Contrary to the ‘polycentricity hypothesis’, we observe a clear hierarchy in the different types of spatial interdependencies in the Randstad, in which the central place model prevails. Furthermore, we do not find evidence for the functional integration of municipalities in the Randstad. We conclude that at this moment the Randstad does not function as a spatially and functionally integrated region, and that spatial economic policy can better focus on smaller regions within the Randstad when urban economic complementarities and integration are desired. This also calls into question the applicability of the urban network concept in general, as the Dutch Randstad is usually seen as a prime example of an economically successful polycentric urban system.