The 2005 growing season marks the tenth year that Bt corn varieties were commercially grown and evaluated at the Northeast Research and Demonstration Farm. Bacillus thuringiensis, commonly known as Bt, is a naturally occurring soil bacterium toxic to European corn bores (ECB) that has been genetically modified and inserted into the corn hybrids. European corn borer incidence is highly variable by year and location. Bt seed corn and insecticide applications are not always warranted each year because of low corn borer populations, due to environmental conditions, several fungal diseases, natural enemies/predators, and parasites. Bt hybrids offer a management option for control of ECB, in which the increased cost of the seed corn must be compared with the cost and effectiveness of insecticide.