Knowledge management systems try to elicit and support the flow of ideas and experiences among groups of employees (sometimes referred to as knowledge communities). Whereas numerous information and communication systems have been developed to support such knowledge exchanges, practical applications have found that technology alone cannot ensure that knowledge will indeed be volunteered and exchanged, and whereas researchers and consultants alike have argued that culture and other human variables constitute key success factors, it is not clear what specific variables are at play, nor what management practices can affect those variables. This exploratory research investigates some of the psychological, organizational and system-related variables that may determine individual engagement in intra-organizational knowledge sharing. Results from a survey of 372 employees from a large multinational show that self-efficacy, openness to experience, perceived support from colleagues and supervisors and, to a lesser extent, organizational commitment, job autonomy, perceptions about the availability and quality of knowledge management systems, and perceptions of rewards associated with sharing knowledge, significantly predicted self-reports of participation in knowledge exchange.