Abstract Strategic Information Systems (IS) planning has become a key management issue for both practitioners and academic researchers because of the increasingly significant impact of IS on organizations' operations and the need for many to develop a long-term vision that will enable IS to play a more strategic role. This study addresses a variety of issues related to IS planning including analysing the planning practices of organizations, their impacts on organizations, and the effects of some organizational / environmental factors on IS planning practices. A large-scale field survey of IS planning practices of 245 U.S. firms provided the data for the study. The results indicate that most organizations have some form of IS planning, but there is wide variation in the planning practices among organizations. The information input from business plans and planning resources is found to significantly influence the quality of the planning process. The quality of the planning process, in turn, significantly influences the contributions of IS to an organization's performance. The role of IS in the organization is also found to significantly influence the planning practices in organizations.