This study aims at creating new knowledge about the connections between regional innovation systems, the enterprises they enclose, and their individual employees in order to better understand the enterprises' innovation processes. A particular focus is directed at the interaction of these employees both within their own enterprises and with individuals and institutions outside them, along with the types of knowledge being involved, and their function in the innovation process. Two research questions are posed: (1) What sort of interaction takes place between individuals inside and outside of an SME when it innovates, within the context of an RIS? and (2) What types of knowledge are involved in this interaction, how are they developed and shared, and what is their function in the innovation process? The study is designed as a qualitative, explorative case study of nine small-and medium-sized enterprises in a Norwegian region. Interaction with customers was identified as the most significant form of interaction driving innovation, and practical knowledge was judged more important than scientific knowledge. This practical knowledge, moreover, was seen as comprising not only production skills but also the practical lifeworld knowledge of customers, and cooperative skills. In addition, a high degree of employee participation in workfloor decisions was judged to promote the innovation process. The paper argues for a revision of the notion of a regional innovation system that takes greater account of these dimensions. Four implications for policy are emphasized: (1) stimulating userproducer interaction within a regional innovation system, (2) involving the right employee groups, (3) utilizing the full potential of various types of practical knowledge, and (4) promoting employee participation within enterprises.