Opinions are plentiful but data are scarce on the potential health risks of genetically modified (GM) food crops. Novel methods and concepts are needed to probe into the differences between conventional and GM crops and into the safety of the genetic techniques used in developing them. So far the preferred approach of the industry has been to compare the makeup of GM and non-GM crops: when they are not significantly different, the two are regarded as ?substantially equivalent? and the new ones are patented without animal testing. Yet ?substantial equivalence? is an unscientific concept and there are no legally binding rules on how to establish it. Insufficient knowledge about basic gene functions, the complexity of metabolic pathways, and the ecological implications of even modest genetic modifications are all making GM crops harder to sell in developed countries, and they are now being dumped on the poorest ones.