As the adverse consequences of the policies of input subsidy and increasing food-grain procurement prices became prominent in Indian agriculture, researchers and policy makers documented the need for policy changes. For sustaining production of rice, there are now calls for shift of emphasis from large farmers in Green Revolution areas in Northwest India to small and marginal farmers in Eastern and rain-fed areas, where returns to both labor and capital are high and potentials for exploiting the existing technology are yet largely untapped. A major constraint on exploiting such potentials in parts of Eastern India such as the Brahmaputra Valley is paucity of irrigation. While investment for expanding irrigation capacity is needed, it is equally important to put necessary institutions in place to ensure that the installed capacity is effectively utilized. This study based on survey of 172 farms from three agro-climatic zones of the Brahmaputra Valley has found that farmers' control over management and operation of irrigation system is crucial in determining their success in effectively using irrigation in terms of level and intensity of productivity increasing practices associated with irrigation. The study hence suggests that to improve effectiveness, and thereby reap higher social returns on public investment on irrigation, involvement of farmers in operation and management of public sector irrigation systems should be secured. In view of the effectiveness of small-scale private tube-wells and the abundance of ground water reserves in the Brahmaputra valley, facilitation of private investments in such sys tems is recommended for expanding total irrigation capacity.