Strategic information systems planning (SISP) remains a top concern of many organizations. Accordingly, researchers have investigated SISP practice and proposed both formal methods and principles of good practice. SISP cannot be understood by considering formal methods alone. The processes of planning and the implementation of plans are equally important. However, there have been very few field investigations of these phenomena. This study examines SISP experience in 27 companies and, unusually, relies on interviews not only with IS managers but also with general managers and line managers. By adopting this broader perspective, the investigation reveals companies were using five different SISP approaches: Business-Led, Method-Driven, Administrative, Technological, and Organizational. Each approach has different characteristics and, therefore, a different likelihood of success. The results show that the Organizational Approach appears to be most effective. The taxonomy of the five approaches potentially provides a diagnostic tool for analyzing and evaluating an organization's experience with SISP.