The recent success of agricultural production in the Office du Niger irrigation scheme in Mali, linked with the modernisation of this scheme over the past twenty years and facilitated by a favourable economic and institutional context, has prompted a debate on the opportunity to extend this 74,000 ha system. The views of the different stakeholders converge on the necessity to have more irrigated lands, but there is a passionate on-going debate on the objectives of the extension - producing more rice for domestic consumption and the export markets or providing the necessary conditions to ensure the viability of the existing farm holdings - and on the planning and implementation of this extension programme. This latter aspect relates principally to the financing of the extension programme, the land tenure status provided to farmers, sharing the water of the Niger river, and to the environmental impact of these extensions. The paper illustrates how the extension of the irrigation system should be integrated in a larger regional rural development planning process.