The practice of developing knowledge management systems in organizations is hindered by a lack of research into (a) what is a knowledge management system, (b) how to develop a knowledge management system in practice, and (c) what role (if any) information technology should play in supporting a knowledge management system. Hence the use of ad hoc, proprietary approaches by practitioners. This paper addresses this gap in research and in practice by presenting five principles from a set of 12 that that emerged through a grounded theory study of the practice of developing knowledge management systems in organizations. The paper focuses on how each of the principles (i) emerged from, and was validated in, evidence collected from developing knowledge management systems, (ii) is connected to related work in the literature, and (iii) informs the practice of developing knowledge management systems. The principles have fundamental implications for the practice and research of developing knowledge management systems in an organizational context. In practice, the principles offer practitioners useful insights into developing knowledge management systems in a way that delivers value to organizations. In research, the principles address several problematic aspects of the literature, particularly concerning divergence, fragmentation and inconsistencies in definitions for knowledge management systems, the purpose for developing knowledge management systems and the role of IT in supporting knowledge management systems. Furthermore, the paper helps distinguish between information systems, which are often used in knowledge management and knowledge management systems whose characteristics, according to the principles presented are very different.