Since 1990s genetically modified foods began to appear in the market place. The most common genetically modified products are soy bean, corn, cotton and canola and the most important genetically modified characteristics are herbicide tolerance and insect resistance. Worries about safety of genetically modified foods led to establishment of labeling rules. Since 1997 based on regulations of European Committee, labeling policy of genetically modified foods has been developed. Those in favor of labeling emphasize consumer's right to know what is in their foods. The majority of opponents believe labeling has high cost and eventually will lead to rejection of genetically modified foods by consumers. This article talks about different aspects of labeling for genetically modified foods.