Transactive memory systems (TMS) are systems of directories that are used to locate and use knowledge in groups. Previous research indicates that, by supporting group cognitive activities, TMS are important determinants of group performance. This paper applies the concept of TMS to knowledge sharing in organizations. The three process dimensions of TMS – directory maintenance, information storage and information retrieval – were used to identify the characteristics of TMS in a case study organization. TMS directories are stored in several types of media, and the processes for maintaining and using these directories varies. The authors conclude that organizational knowledge sharing may be assisted by information systems developed to support TMS, and suggest how an understanding of the nature of an organization’s TMS might be used to design information systems and management interventions to improve knowledge sharing.