This paper examines the extent to which systematic differences in performance across firms can be explained by the different sets of capabilities mastered by firms. Cluster analysis is used to group firms based on the degree of capability accumulation along three dimensions: manufacturing, R&D and marketing. Sixty-seven Spanish domestic pharmaceutical firms are studied, focusing on the period 1990?1997. Our findings indicate that five clusters can be identified. Firms with better performance indicators are those that manage to generate capabilities that are uncommon among competitors?particularly capabilities in product development.