China's capacity to increase production and economic efficiency in agriculture in the 1980s will depend on its ability to adopt appropriate policies and to overcome technical and environmental constraints. Insistence on local and regional self-reliance led to an overemphasis on grain production at the expense of cash crops (oilseeds, cotton, soybeans, etc.) and fodder acreage. The effectiveness of policy changes will depend on the ease with which technical and environmental constraints can be overcome. Approximately 50 percent of China's gross agricultural product is derived from grain, and grain provides close to 90 percent of all calories consumed in China. Until recently there have been few data on which to judge the past performance or future potential of Chinese agriculture. Even now, available data are spotty and frequently of variable quality, rendering any attempts at quantitative analysis suspect. For such a large and climatically diverse country, national aggregates provide no clear understanding of technical constaints or growth potentials.