The aim of this paper is to analyse the effects of human capital, advanced manufacturing technologies (AMT), and new work organizational practices on firm productivity, while taking into account the synergies existing between them. This study expands current knowledge in this area in two ways. First, in contrast with previous works, we focus on AMT and not ICT (information and communication technologies). Second, we use a unique employer-employee data set for small firms in a particular area of southern Europe (Catalonia, Spain). Using a small firm data set, allows us to analyse the particular case of small and medium enterprises, since we cannot assume they have the same characteristics as large firms. The results provide evidence in favor of the complementarity hypothesis between human capital, advanced manufacturing technologies, and new work organization practices, although we show that the complementarity effects depend on what type of work organization practices are used by a firm. For small and medium Catalan firms, the only set of work organization practices that improve the benefits of human capital and technology investment are those practices which are more quality oriented, such as quality circles, problem-solving groups or total quality management.