A 'model of decentralised concentration' has evolved in the region of BerlinBrandenburg in response to the European principle of polycentric development for urban regions. The paper describes strategies which seek to implement this new regional planning guideline. The formation of an urban forum as a co-ordinating body has initiated a course of development which attempts to link aspects of both horizontal and vertical policy co-ordination within a framework of territorial integration (networking). The paper analyses this innovative instrument of urban and regional development. The authors focus on the process of co-operation, beginning with the looser form practised in the urban forum by the towns which participated and evolving towards de ned contractual and institutional relations in the form of a networked urban workgroup. Finally, they evaluate the objectives achieved and the nancial and legal instruments applied.