Wheat with major gene resistance to Hessian fly can successfully defend itself from Hessian fly attack, but at what cost to plant fitness? Our research objective was to explore the possible costs of R gene resistance. We examined the possible negative linkage and pleiotrophic effects of the R gene, as well as the costs to the plant of the combined effects of Hessian fly larval attack and plant defense. To accomplish this we developed a two-part project. First, we examined three near-isogenic hard red winter wheat genotypes with the H6, H9, and H13 R genes and compared their fitness to their recurrent parent 'Newton' in the absence of Hessian fly. Second, we studied the combined effects of Hessian fly larval attack and successful plant defense on attacked versus un-attacked plants. The R gene containing genotypes we used for both parts of the project were developed by six backcrosses and are 98.44% similar to 'Newton'. We initially conducted our examination of costs under greenhouse conditions in the winter of 2003/2004. In the summer of 2004, our work was repeated under field conditions. Measures of fitness recorded for both portions of the project were primarily components of yield, and they include tiller number, seed number, and total seed weight.