The article questions the reasons explaining the localized character of innovative firms' founding. Based on an in-depth qualitative field study reconstructing the founding mechanisms of German biotechnology firms, it demonstrates that localized knowledge spillovers - which are frequently invoked in the literature- do not play such a crucial role in localization choices made by entrepreneurs. Obtaining, successively, the various resources needed to build up their company leads founders and managers to stay in the region where they have worked so far. Social structures (organizations and programs) that are able to bring entrepreneurs to the required resources in a more depersonalized way than social networks are a key factor in this respect.
