This paper explores the relationships between internal R&D and external knowledge acquisition as business innovation strategies. Drawing on absorptive capacity framework (Cohen and Levinthal, 1990), we distinguish and empirically evaluate two possible relationships: coexistence and complementarity. The analysis is based on a large sample of manufacturing firms taken from the Spanish Survey of Technological Innovation 2004. Our results show coexistence between internal R&D and external knowledge acquisition but they do not provide evidence that these activities are complementary with respect to influencing innovation performance. In other words, although our results suggest that internal R&D activities are associated with a greater use of external knowledge sourcing strategies, they do not seem to have synergistic effects to develop new products.Este artículo analiza las relaciones existentes entre la generación y la adquisición externa de conocimiento como estrategias de innovación empresarial. Para ello, y utilizando el concepto de capacidad de absorción (Cohen y Levinthal, 1990) como marco de referencia, se distinguen y se analizan empíricamente dos posibles relaciones: coexistencia y complementariedad. El estudio es realizado sobre una muestra amplia de empresas manufactureras españolas, empleando los datos derivados de la Encuesta sobre Innovación Tecnológica del año 2004. Los resultados muestran que en el contexto analizado, las actividades internas de I+D y las estrategias asociadas con la adquisición externa de conocimiento son estrategias coexistentes, pero no complementarias. En otras palabras, si bien las actividades internas de I+D facilitan la identificación y adquisición de conocimiento externo, no se encuentra evidencia a favor de que dichas actividades tengan un efecto sinérgico para el desarrollo de nuevos productos.This paper explores the relationships between internal R&D and external knowledge acquisition as business innovation strategies. Drawing on absorptive capacity framework (Cohen and Levinthal, 1990), we distinguish and empirically evaluate two possible relationships: coexistence and complementarity. The analysis is based on a large sample of manufacturing firms taken from the Spanish Survey of Technological Innovation 2004. Our results show coexistence between internal R&D and external knowledge acquisition but they do not provide evidence that these activities are complementary with respect to influencing innovation performance. In other words, although our results suggest that internal R&D activities are associated with a greater use of external knowledge sourcing strategies, they do not seem to have synergistic effects to develop new products.