Field corn, sweet corn, popcorn, and soil from Iowa fields were analyzed for residues of terbufos (Counter®), O,O-diethyl S-[(tert-butylthio)methyl] phosphorodithioate. A granular formulation (Counter 15-G) was applied at the time of planting as a band or furrow treatment of 1, 2, and 4 lb AI/acre. Residues of terbufos, expressed as the fully oxidized sulfone (O,O-diethyl S-[(tert-butylsulfonyl)methyl) phosphorothiolate), in field corn forage ranged from a high of 0.43 ppm 40 days post-treatment (4-lb furrow application) to a nondetectable amount 60 days post-treatment (1-lb band application). No detectable residues were found in field corn grain, plus cob, harvested for silage (100 days post-treatment), and quantities in stover of the same maturity showed only 0.01–0.04 ppm. Analyses of fully mature grain (160 days) showed no residues. Quantities of terbufos in soil where field corn was grown ranged from 78 ppm immediately after application (4-lb furrow application) to 0.3 ppm 160 days post-treatment (1-Ib band application). Sweet corn grain and popcorn grain sampled at edible maturity showed no residues of terbufos even though 10–14 ppm still were in the accompanying soil.