China is the world's largest producer and consumer of food. In the past, China's governmental policy advocated regional self-sufficiency in agricultural production, and it is generally believed that regional self-sufficiency was enforced at high economic cost. However, this changed with the 1979 economic reforms which encouraged some regional specialization. It is expected that there may be further shifts in regional production patterns and interregional trade flows. This article uses data on land productivity to test for regional comparative advantage, and it provides some empirical evidence on provincial comparative advantage in cotton versus grain production in China.