In the l930s the Zhejiang government promoted the introduction of improved cotton breeds. The annual output of improved cotton formed only about O.3 per cent of the total cotton output in China, but this was sufficient to meet the demand from cotton mills in Zhejiang. In that sense, therefore, tlte cotton improvement campaign was effective. But some peasants resisted the cotton improvement campaign and this resulted in riots. This paper examines the possibility that the reproduction-structure of the conventional cotton industry was the main cause behind resistence to improved cotton breeds. That is, the peasants who resisted improved cotton breeds were those who were growing conventional native cotton to spun into yarn which they wove into cloth. The improved cotton was more suited for machine-spinning in cotton mills than conventional native cotton. On the other hand, conventional cotton was better for peasants working at home by traditional methods to spin their own yarn. In other words, it was not the peasants who profited from the cotton improvement campaign but the capitalists of the cotton industry.