All too often development plans underplay, or disregard, attempts to change traditional marketing systems. Where such plans do recognise the importance of marketing in development, other weaknesses are often apparent. Planners seldom seem to recognise the systematic nature of marketing and those aspects of structure and process which serve to shape the way in which the system functions. Further development plans often appear merely an articulation of political philosophy and/or economic considerations, and sufficient regard is seldom paid to those socio-cultural factors which impact in the development process. These ideas are explored in the present paper through an examination of plans to develop the Tanzanian Lake Victoria fisheries. Sections: the traditional fish marketing system (overview, structure, processes) – development of the Lake Victoria fisheries – an appraisal of fisheries development plans: strategy and the agent of change – possible results of proposed change strategies – government as an agent of change – conclusion. Fig., notes, ref.