Quantifying the presence of an edge effect in the distribution of gypsy moth,Lymantria dispar(L.) egg masses is important in sampling egg masses to determine unbiased population density estimates. Egg masses were counted on trees along the forest edge and on trees two chains (40.2 m) in from the forest edge in 16 locations in Virginia. Edge trees had about 2.4 times more egg masses than interior trees. The edge side of edge trees had about 3.2 times more egg masses than the edge side of interior trees and about 4.8 times more egg masses than the interior side of these same trees. Samples taken at or near the forest edge will overestimate population levels, or they will increase the probability of incorrectly classifying populations as being over thresholds if applied to larger areas using currently available sampling methods. In the areas studied, the edge effect on the distribution of egg masses is a function, in part, of the morphology of edge trees. The bias of an edge effect may not be a consideration when the edge area itself is the area of interest.