The world city network as deﬁned by advanced producer services is not the only way in which contemporary cities are linked across the world. In this book it is argued that ﬁnancial and business services are currently leading economic sectors that are dominating world city network formation, but ﬁrms in these sectors are by no means the only ‘world city networkers’. The enabling technologies in computers and communications may have been stimulated in many of their advances through the demand created by ﬁnancial and business services, but the technologies remain available to others. Worldwide communities relating to environmental issues and other global campaigns have created networks through non-governmental organizations (NGOs). All such institutions are instrumental in linking up their activities across the world, largely through cities. In fact, some of the larger NGOs have ofﬁce networks as large and widespread as those of many global service ﬁrms; they are creating their own interlocking network of cities.