1 The impact of internal and external networks on innovation performance. Evidence from the UK Community Innovation Survey Marion Frenz and Grazia Ietto-Gillies 1 Abstract The paper explores the impact of internal and external networks on the innovation performance of enterprises operating in the UK. It uses information from the UK Community Innovation Surveys. The national and international dimension of the networks are explored and tested for their impact on innovation performance. We find that both internal and external networks are positively associated with innovation performance and that the effects are greatest when an enterprise belongs to an international internal network and, at the same time, cooperates with national organizations. JEL classification: F23; O12, 19, 33, D85 Keywords: Networks: internal and external; Cooperative agreements; Innovation; Internationalization; Community Innovation Survey UK. 1 Marion Frenz, School of Management and Organizational Psychology, Birkbeck, University of London, Malet Street, London WC1E 7HX: m.frenz@bbk.ac.uk; Grazia Ietto-Gillies, London South Bank University, 103 Borough Road, London SE1 0AA: iettogg@lsbu.ac.uk.