The production of foods with genetically modified organisms (GMOs) has risen rapidly over the past three decades to comprise nearly 90% of crops grown in the United States today. Currently, there are no mandates for labeling foods containing GMOs. GMO agricultural crops contain the insertion of genes encoding for pesticides, pesticide resistance, growth factors, or other substances not normally present. In addition to the foreign genes that are inserted, hundreds to thousands of mutations disrupt normal genes in GMO plants. Recently, animal studies have demonstrated toxicity of GMO foods causing organ failure, infertility, carcinomas and death. The FDA requirement of ingredients added to foods being labeled on the product is not applied to GMO foods, precluding the consumer's right to know. GMOs provide an economic incentive to companies because the seeds can be patented, driving up costs and creating the potential for monopolies. Herbicide-resistance conferred by GMOs has resulted in higher pesticide applications, which correlate with higher human cancer rates, and the emergence of pesticide-resistant weeds and insects. GMO toxins are spreading into non-target insects, waterways and aquatic organisms, with toxicity to non-target organisms and resultant contamination of disparate ecosystems in the food chain. The appropriateness of mandatory GMO labeling of foods in the United States is discussed.