Transactive memory system is a term from group psychology that describes a system that helps small groups maintain and use personal directories to allocate and retrieve knowledge. Such systems have been observed at the level of whole organizations, suggesting that they provide a means for conceptualizing the exploitation of organizational memory. In this paper, I describe a longitudinal investigation of a global engineering consulting firm in which I used inductive analysis of interview data to map and then develop a conceptual entity-relationship model of organizational memory. This model formed the basis for a transactive directory to facilitate knowledge retrieval and allocation in the firm