Organisation development literature is replete with writings on how to improve organisational effectiveness. While this is useful, actions in the real world often formally involve multiplicity of organisations especially if one examines public delivery systems, public programmes and large construction and technological projects. While matrix organisation and project management have been invented to cope with issues arising out of such situations by managers (not by academics) this paper argues that these approaches do not adequately deal with boundary issues. Therefore, it argues that one has to develop a concept of inter-organisational effectiveness and using the concept of boundary, develop strategic interventions for inter-organisational effectiveness. It is suggested that failures of public delivery systems, public programmes and large construction and technological projects could be due to failures in understnading these two key concepts and failures in making appropriate strategic interventions.