Interactions of the Hessian fly (Mayetiola destructor Say) with host plants are characterized by plant defense via R genes and insect adaptation via modifications in corresponding avr genes. Commonly, researchers report that R-gene defended wheat genotypes do not suffer growth deficits when attacked by avirulent Hessian fly larvae. However, growth responses of R gene plants have not been measured precisely, especially growth responses of actively-growing leaves. Moreover, growth responses have not been measured during the early phases of larval attack. We addressed the following hypothesis: R gene-defended wheat genotypes grow normally when attacked by avirulent larvae regardless of the R gene that is expressed. To test this hypothesis we infested plants of four near-isogenic lines, one without an R gene and three others, each with a different R gene (H6, H9 or H13). Wheat seedlings, either with no larvae or large numbers of larvae (ca. 50 larvae), were destructively sampled at 2, 7, and 15 days after larvae initiated their attack. Length measurements were taken for each leaf. The null hypothesis was not supported. All three R gene wheats exhibited growth deficits associated with larval attack. These deficits differed from those of non-R gene plants because they were smaller and limited to the 3rd and 4th leaf and did not extend to the 5th leaf and tillers. H6 differed from H9 and H13 because it exhibited greater deficits as well as lesions and dead larvae at initial attack sites.