A. R. Schwember. 2008. An update on genetically modified crops. Cien. Inv. Agr. 35(3):231-250. Genetically modified (GM) crops were introduced in the mid 1990s and two principal transgenic technologies currently domínate the market, herbicide-tolerant (HT) crops and insect-resistant crops (Bacillus thuringiensis (Bt) crops). HT crops have simplified weed management practices, reduced crop production costs, and have had positive effects on the environment. However, there are concerns about the potential development of weeds resistant to glyphosate, the main herbicide employed with HT crops. A second major worry associated with the use of HT crops is the potential introgression of genes from GM crops into wild relatives (i.e. gene flow) and its potential impact on natural ecosystems. Bt crops have increased yields and reduced the use of insecticides, providing benefits for human health and the environment. However, the potential development of resistance to the Bt toxin by insect pests and the indirect damage of Bt toxins to non-target species are major concerns related to their use. Different strategies to mitígate and elimínate the problems associated with the use of GM crops are discussed in the paper. The next step in plant biotechnology is the reléase of nutrí ti onally-enhanced components in seeds that will benefit humans directly.