In this article, we have empirically analyzed the effects of Bt cotton on pesticide use and productivity in Argentina. The farm survey reveals that the technology leads to a considerable decline in pesticide application rates. On average, adopting farmers use 50% less insecticides on their Bt plots than on plots grown with conventional cotton. Almost all of these reductions occur in highly toxic chemicals, with concomitant positive effects for the environment.Moreover, Bt adopters benefit from significantly higher yields, which is due to insufficient pest control in conventional cotton. In an international comparison, Argentine farmers use relatively little amounts of pesticides, so the yield gains of Bt cotton are higher than in many other countries.