Recent developments in innovation theory and policy have led policymakers to assign particular importance to supporting networks of cooperation among heterogeneous economic actors, especially in production systems composed of small and medium enterprises. Such innovative policies call for parallel innovations in policy analysis, monitoring and assessment. Our analysis of a policy experiment aimed at supporting innovation networks in the Italian region of Tuscany intends to address some issues connected with the design, monitoring and evaluation of such interventions. Combining tools from ethnographic research and social networks analysis, we explore the structural elements of the policy programme, its macroscopic impact on the regional innovation system, and the success of individual networks in attaining their specific objectives. This innovative approach allows us to derive some general methodological suggestions for the design and evaluation of similar programmes.