International audience Several papers contributed to popularize the idea that the specific advantages of Bt-cotton have permitted the successful diffusion of Genetically Modified Cotton in China. The efficiency of Bt-cotton however fluctuates between cotton production regions. In Jiangsu Province, along the Yangtze River Valley, there is not really yield increase, reduction in insecticide control is small and, globally, there is no income gain associated specifically to the use of Bt-cotton. The use of Bt-cotton is nevertheless almost general there. A more comprehensive approach, beyond focussing on the Bt-cotton specific effects, helps to explain this apparent paradox. In Jiangsu province, the diffusion of Bt-cotton has benefited from its integration into hybrid cultivars which are perfectly adapted to the profitable transplanting technique. This Chinese case indicates that the appraisal of Bt-cotton use in other countries should consider the extent to which this use would be compatible (or not) to existing production technologies. In China, the commercialisation of Bt-cotton has induced the modernization of the planting seed market. Farmers firstly benefit from this process before suffering now from the resulting high pricing strategy. If Bt-cotton is to give more than it takes from farmers, some regulation of the seed market is desirable.