In the brave new world of genetic engineering, Dean DellaPenna, a plant biochemist at Michigan State University, envisions this cornucopia: tomatoes and broccoli bursting with cancer-fighting chemicals and vitamin-enhanced crops of rice, sweet potatoes, and cassava to help nourish the poor. He sees wheat, soy, and peanuts free of allergens, bananas that deliver vaccines, and vegetable oils so loaded with therapeutic ingredients that doctors "prescribe" them for patients at risk for cancer and heart disease. DellaPenna believes that genetically engineered foods are the key to the next wave of advances in agriculture and health. While DellaPenna and many others see great potential in the products of this new biotechnology, some see uncertainty, or even danger. In North America and Europe, the value and impact of genetically engineered food crops have become the subjects of intense debate, provoking reactions from unbridled optimism to fervent political opposition. Most people in the United States don't realize that they've been eating genetically engineered foods since the mid-1990s. And in fact, genetic modification is much older than that, but the technique of genetic engineering is new and quite different from conventional breeding. Traditional breeders cross related organisms whose genetic makeups are similar. In so doing, they transfer tens of thousands of genes. By contrast, today's genetic engineers can transfer just a few genes at a time between species that are distantly related or not related at all. Whether biotech foods will deliver on their promise of eliminating world hunger and bettering the lives of all remains to be seen. Their potential is enormous, yet they carry risks and we may pay for accidents or errors in judgment in ways we cannot yet imagine. However, the biggest mistake of all would be to blindly reject or endorse this new technology. If we analyze carefully how, where, and why we introduce genetically altered products, and if we test them thoroughly and judge them wisely, we can weigh their risks against their benefits to those who need them most.