The Russian wheat aphid (Diuraphis noxia (Mordvilko)) is a severe pest of wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), and other small grains and grasses in the High Plains region of the United States. Cumulative economic losses from Russian wheat aphid infestation in wheat and barley in the US have been estimated at nearly $1 billion since 1987. Nearly 60% of these losses have occurred in the Texas and Oklahoma Panhandles, northeastern Colorado, western Kansas, and southwestern Nebraska. The objective of this study was to determine the yield loss due to Russian wheat aphid infestation in wheat under field conditions. A total of 10 fields (one field in 2004, three fields in 2005, and six fields in 2006) were sampled. The results showed that yield losses in wheat due to Russian wheat aphid infestation ranged from 61 to 84% when compared to uninfested wheat.