This paper reappraises the managerialist model of organizations which underpins most current approaches to IS planning. There is much criticism of the managerialist model as a flawed approach because it assumes that organizations are unitary entities which act rationally in the pursuit of system goals. This model ignores the different interests among individuals and groups in an organization and the significance of conflict and power in shaping organizational practices. Because IS planning constitutes a major site of organizational activity, it is important that research in this area theorizes organizations in an inclusive and informed way. Insights from Critical Social Theory can help analysts of the IS planning process understand the dynamics of that process more fully. It provides a framework for an improved research agenda to gain this understanding.