Farmers are well aware that corn grain yields vary from plant to plant. However the extent of this variability across a range of different environments has yet to be evaluated. This study was intended to evaluate by-plant corn yield variability over a range of production environments and to evaluate the relationships among the mean grain yield, standard deviation, coefficient of variation, and yield range. A total of forty-six 8 to 30m corn transects were harvested in Argentina, Mexico, Iowa, Nebraska, Ohio, Virginia, and Oklahoma from 2002 to 2004. By-plant corn yields were determined from all sites in different countries and states, plant to plant variation in corn yield averaged 2765 ks ha-1 (44.1 bu ac-1). At sites with the highest average corn grain yield [11478 and 14383 kg ha-1 (67 bu ac-1)and 2962 kd ha-1 (47 bu ac-1)] the average grian yield range increased, the standard deviation also increased within each row. Also, the yield range (maximum corn grain yield minus the minimum corn grain yield per row)was found to increase with increasing yield level. This shows that regardless the yield level, the plant to plant variability in corn grain yield can be expected and averaged more than 2765 kg ha-1 over the duration of years and sites. Average plant yield from distances greater than 0.5 m removed the extreme by-plant variability. Therefore, the scale for sensing and treating factors affecting yield should be less than o.5 m. Production methods that homogenize plant stands and emergence should decrease plant to plant variation and will lead to increased yields.