Advocates of the use of genetic engineering techniques in agriculture contend that this new biotechnology promises increased productivity, better use of natural resources and more nutritious foods. Opponents are concerned about potentially adverse implications for the environment and food safety. In response to consumer reactions against genetically modified (GM) foods, in some countries crop production is being segregated into GM and non-GM varieties. This analysis finds that world markets for maize and soybeans adjust well to these changes and also that developing countries will divert their trade patterns in response to preference changes in important trading partner countries.