Corn (Zea mays) is one of the most important crops, both in the United States and internationally. A major limitation in corn production across the Southern U.S. and other parts of the world is accumulation of aflatoxin, a toxin produced by the fungi Aspergillus flavus. Aflatoxin is a known carcinogen toxic to both humans and livestock when ingested. Currently no commercial hybrids are fully resistant to aflatoxin contamination, but genetic variation for resistance has been exhibited among inbred lines and hybrids. Aflatoxin contamination is difficult to evaluate in the field because of varying amounts of source inoculum and dependency on favorable environmental conditions. Corn hybrids in growing areas in South and Central Texas are exposed to drought and high temperatures after flowering, conditions that are conducive to aflatoxin production. Our objectives are to 1) estimate the response of experimental and commercial hybrids to aflatoxin across a range of environments; 2) identify the hybrids within each group that exhibited the lowest levels of contamination; 3) analyze the relationship between agronomic performance and aflatoxin accumulation; and 4) determine how genotype x environment interactions affect target traits. Three independent experiments of 25 hybrids (yellow, white and high lysine hybrids) have been planted during the spring of 2005 at ten representative locations of corn producing regions in Texas, both rain fed and irrigated. Field plot design is alpha lattice with 3 replications. Inoculations with Aspergillus flavus of 10 plants per plot will be done at each location using the silk channel inoculation method. Hand harvested samples prior to combine harvest will be used to quantify aflatoxin and measured kernel traits. Results will be presented and discussed during the meetings presentation.