In this paper we analyze the effects that foreign-owned firms have on the Spanish lndustrial Sector, considering two different aspects. First, we measure the differences between domestic and foreign-owned firms in their technological activities, international trade, assets and performance. Secondly, we study the spill-overs that foreign-owned firms have over the technological activities and efficiency of domestic-owned firms, as well as on the degree of competition in Spanish industrial markets. Our results show the quantitative and qualitative importance of foreign-owned firms in Spanish manufacturing sectors, but the spill-overs of foreign-owned firms could not be strongly confirmed.

Keywords: foreign-owned firms, domestic-owned firms, spill-overs.