The objective as to determine the effect of Bt corn on the performance of steer calves fed whole plant corn silage (WPS)during the growing phase follo ed by a high grain finishing diet. During the 1998 (yr 1) and 1999 (yr 2) cropping seasons, alternating 6.8 ha fields (8 in yr 1 and 6 in yr 2) were planted to either Bt (Yieldgard) or the near isogenic parental hybrid (Pioneer 3489 in yr 1 and Pioneer 34E79 in yr 2). Prior to harvest, perimeter rows were removed to reduce the possibility of feeding cross-pollinated hybrids. Fifty-six Angus and Simmental sired steer calves (300 kg),1 month postweaning, were randomly allotted by eight and breed type into eight pens of seven steers. They were fed the WPS diet for 89 d in yr 1 and 85 d in yr 2. The finishing diet contained 75% dry rolled corn, 15% whole plant corn silage, and 10%suppl. on a DM basis. The finishing phase was 101 d in yr 1 and 84 d in yr 2. During the WPS phase of yr 1, ADG and DMI did not differ (P >.05) between groups while feed/gain averaged 7.08 and 6.40 between Bt and control steers (P <.05). Steer performance during the WPS phase of yr 2 did not di .er (P >.05). There were no significant differences in ADG, DMI, or feed/gain during the finishing phases (P >.05). Combining the yr 1 WPS and finishing phases, ADG averaged 3.18 and 3.30 kg/d (P >.05), DMI averaged 9.80 and 9.71 kg/d (P >.05), and feed/gain averaged 6.78 and 6.47 (P <.05) among Bt and control steers. There were no overall performance differences (P >.05) during yr2 (ADG, 3.14 vs 3.21 kg/d; DMI, 9.52 vs 9.79 kg/d; and feed/gain, 6.66 vs 6.72). Steers were harvested on multiple dates when it was estimated that 75% of a load would grade USDA Choice. There were no differences in carcass characteristics (P >.05). Results indicate that there are no major differences in the feeding value of grain from Bt corn and the near isogenic parental hybrid when fed to beef steers on a high grain finishing diet.