To evaluate the potential of Bacillus thuringiensis (Bt) Cry1F protein accumulation in soil, transgenic corn containing event DAS-01507-1 encoding the cry1F gene was grown in three field sites for 3 consecutive yr, and the corn plants were incorporated into the soil through postseason tillage or no tillage each year. Soil samples were collected from these fields, and the level of Cry1F protein in these samples was determined using an enzyme-linked immunosorbent assay (ELISA) with a synthetic invertebrate gut fluid as an extraction buffer. The ELISA was validated in soil matrices over the concentration range of 18-180 ng/g dry weight, with a limit of detection of 4.5 ng/g dry weight. The assay was shown to have good accuracy and precision. No detectable Cry1F protein was found in any of the soil samples collected from the Cry1F corn fields. Soil also was bioassayed, and no biological activity was observed against Heliothis virescens neonates. These results indicate that the level of Cry1F protein accumulated in soil after 3-yr continuous planting of transgenic Cry1F corn is negligible.