Expectations play a powerful role in driving technological change. Expectations are often encapsulated in narratives of technological promise that emphasize potential benefits and downplay potential negative impacts. Genetically modified (GM, transgenic) crops have been framed by expectations that they would be an intrinsically ‘pro-poor’ innovation that would contribute powerfully to international agricultural development. However, expectations typically have to be scaled back in the light of experience. Published reviews of the socio-economic impacts of GM crops among poor, small-scale farmers in the developing world indicate that these effects have been very mixed and contingent on the agronomic, socio-economic and institutional settings where the technology has been applied. These conclusions should modulate expectations about the pro-poor potential of GM crop technology and focus attention on the conditions under which it might deliver substantial and sustainable benefits for poor farmers. However, the idea of GM crop technology as an intrinsically pro-poor developmental success story has been sustained in academic, public and policy arenas. This narrative depends upon an analysis that disembeds the technology from the technical, social and institutional contexts in which it is applied. Agricultural development policy should be based on a more rigorous and dispassionate analysis, rather than optimistic expectations alone.