This paper proposes a model of knowledge management system (KMS) evolution leading to the realization of competitive advantages as promised throughout the KM literature. Using a framework developed to study e-business capability evolution, the paper presents a case study of a KMS specifically created to enhance an organization?s ability to compete for science and technology research funds. The case study is then used to develop an evolutionary model for KMS success based on increasing embeddedness and mass of knowledge. The paper ends with a discussion of how this new model integrates with existing KM literature in two critical areas: the integration of tacit knowledge, and the evaluation of KMS success.