A decomposition model has been used to measure sources of individual and aggregate crop output growth between 1967-70 and 1981-84. Growth in output has been attributed to changes in area, yield and area-yield interaction and the area effect has been further attributed to changes in net area, cropping intensity, cropping pattern and their interactions. Results show that over 50 percent of increased output has come from increased yield and about 33% from increased area. The area-effect has resulted almost entirely from increased cropping intensity. Substitution of high value crops for low value crops has made some positive contribution but that has been balanced by the effect of decrease in net crop area. In the future, productivity growth through increased irrigation and complementary input use should assume greater importance because net crop area will continue to decline and cropping intensity may soon level off.