Corn (Zea mays, L.) hybrids exhibit different yield responses to defoliation timing and rates. There is limited data on the effect of row width on defoliation in modern hybrids. A two-year experiment was conducted in Lexington, Kentucky (38° 7'42.57"N, 84°29'27.91"W), in a Maury Silt Loam with 2 to 6% slopes. The objective of this experiment was to determine the effect of corn defoliation in 38- and 76-cm rows. Treatments for this experiment include: control (no defoliation) and defoliation events at growth stage V7 (100% rate), V14 (50 and 100% rates) and at R2-R3 (50 and 100% rates). Overall, 2012 corn yield in 38-cm rows width was greater than for corn in 76-cm rows. Defoliation at V7-100% resulted in the greatest numerical yield value which was not different than yield for the control. Defoliation within the critical period for yield determination (V14, a few days before anthesis, and R2, about 2 weeks after anthesis) greatly reduced the yield with V14 defoliation resulting in the greatest yield loss. For both defoliation timings, 100% defoliation caused greater yield loss than 50%. Kernel number was reduced most by V14 defoliation. Kernel weight was reduced most by R2 defoliation.