This paper develops an interactional approach to planning in organisations that draws out the relevance of both rationalist and contingent models of planning. The distinction between these two models is developed in the light of the modernist / postmodernist debate to provide a set of theoretical issues to with planning in organisations. These issues are explored in the context of planning carried out in two empirically studied settings, a health authority and a school. The two models are found to provide resources for organisations and participants in these settings, both to proceed with planning activity and to account for it. Neither model is however adequate to describe the process of planning which is always a practical and situated activity whose character emerges in the process of interaction.