Herbicide-resistant and insect-resistant GM crops have been grown in order to save pesticide uses. Although the first years in the USA showed some benefit, further observations could be interpreted as a slow down in pesticide reduction together with the appearance of threats to the sustainability of the GM technology. On the one hand, alternate techniques were improved so as to use less pesticide. On the other hand, the appearance of herbicide-resistant weeds lead to the come-back of heavy herbicide weed control programs. However, the reduction in insecticides was sustained thanks to the setting up of the refuge strategy. The USA experience must be taken into account to design and evaluate the impact of the GM crops on the 'green' policies to reduce the amount of pesticides used in Agriculture.