The labeling of genetically modified foods (GMFs) is the topic of a debate that could dramatically alter the structure of the U.S. and international food industry. The current lack of harmonization of policy across countries makes GMF labeling an international trade issue. The U.S. and Canada do not require GMFs to be labeled unless the GMF is significantly different than the conventional food or the GMF presents a health concern. However, many other countries are requiring GMFs to be labeled. This paper discusses empirical work on the sources and magnitude of benefits and costs from labeling programs, with particular emphasis on the impact of the design of the labeling program on benefits and costs.