A major issue facing managers of Information Systems organizations is the increasing pressure to demonstrate the business value of the firm' s investment in information technology. The working relationship between the IS group and other diverse organizational groups can have a major contribution to increasing IS performance. This paper explores the concept of shared knowledge between IS groups and their line customers as a contributor to IS performance. Shared knowledge is achieved through Ihe mechanisms of mutual trust and influence between these groups. The relationship of mutual trust, influence, and shared knowledge with IS performance is tested empirically using path analysis in a study of eighty-six IS organizations. The results of this study show that shared knowledge mediates the relationship between IS performance and trust and influence and that increasing levels of shared knowledge between IS and line groups leads to increased IS performance. Recommendations are given for ways managers can develop mutual trust and influence between these diverse groups, and therefore achieve higher levels of shared knowledge and IS performance.