The analysis of networks has flourished in recent years offering an original and suggestive framework even for the study of local development phenomena, by focusing both on inner interrelations between local actors and on their outward connections. Different schools have provided crucial insights and have stressed complementary aspects of this issue. Among others, we should mention the Swedish and Anglo-Saxon tradition, which emphasises the notion of ‘industrial network’ (see, inter alia, the works of Axelsson and Easton, 1992 and Batten et al., 1995); the attention paid by Italian scholars to widening and deepening the old concept of Marshallian industrial district (beyond the seminal work of Becattini, 1987, it is worth to refer to two recent volumes edited by Varaldo and Ferrucci, 1997, and Bramanti and Maggioni, 1997); and, obviously, the new approach proposed and developed by Gremi in a long-term research project founded on the concept of innovative milieu (see the opening chapter by Bramanti and Ratti in the present volume).