The Hessian fly, Mayetiola destructor, is an important pest of spring wheat in northern Idaho. The most effective control method is the use of resistant cultivars. However, there is potential for emergence of biotypes capable of attacking resistant cultivars. Utilization of multiple genes for resistance is important in an overall pest management strategy. Eighteen lines derived from crosses of sources carrying the H3 and H25 genes for resistance were evaluated in 2006. Susceptible (Alturas) and resistant checks [Jefferson (H3) and IDO584 (H25)] were also evaluated. Field assessments were done under natural fly infestation and laboratory ones using artificial infestation. Mean number of insects per plant and percent-infested plants were determined. Alturas had 82.5% infested plants in the field and 100% in the laboratory, Jefferson 7.5% in the field and 16% in the laboratory, and IDO584 2.5% in the field and 1.4% in the laboratory. Eight breeding lines showed no infested plants in laboratory tests and also exhibited the best performance in the field. This may indicate the lines carry both the H3 and H25 genes. Given the presence of fly biotypes with virulence against the H3 gene in Idaho, we expected Jefferson to exhibit some plants infected with Hessian fly in both laboratory and field tests. The presence of Hessian fly in IDO584 was unexpected, however, since virulence against the H25 gene has not been reported. This could be due to the presence of some off-type plants in IDO584. Further evaluations are thus, warranted.