A general conceptual framework to explain clustering phenomena based on intangible assets can be established by analysing in depth the spatial implications of the inherent attributes of intangibles. It is possible to list five interconnected characteristics, as follows: knowledge content, non-rivalry, partial excludability, non-tradability and risk and information asymmetries. Analysing whether and how the new and growing importance of intangibles is affecting the traditional theories of clustering and economic geography is a crucial point if one wants to understand them from the point of view of economic theory. The insufficiency of traditional metrics is therefore at the centre of the debate on intangibles. The concept of co-operation and networking among firms has been emphasised in the analysis of the success of the Silicon Valley high-tech cluster. The importance of geographical proximity can be seen with reference to innovation-related intangibles, such as human capital-related and customer-related intangibles. Human capital-related assets also seem to have important implications for the geography of production.