In this paper the general validity of the research area of key factors of success in product development is discussed. To be more specific we argue that validity hinges on the causal relation between success and success factrors a relation that unaccounted for in the empirical studies. The theoretical tradition of the resource-based perspective provides at least to some extent an account of this causality. An important point in the paper is that the key factors of success in the empi studies are not factors causally related to success, but at the most a number of valuable resources and thus the necessary but not sufficient conditions for success. A second issue in the paper is the discussion of how the empirical results may be implemented in firms. The results of the empirical studies show managers where to concentrate their efforts in order to raise the rate of successful products, but in the studies problems concerning implementation are not discussed. When the lists factors of success are interprested as valuable resources and capabilities, we show that some implications on the implementability might be deduced from the resource-based perspective.