Fusarium Head Blight, caused by the fungal pathogen Fusarium graminearum Schwabe, is among the most destructive diseases of common wheat in many wheat growing areas around the world. While chemical control and improved cultural practices can reduce the risk, development of resistant varieties is the most effective method of disease control. Genetic resistance to the disease is quantitatively inherited, and is characterized by forms of tolerance. The major resistance gene discovered and deployed across the upper Midwest, and most wheat growing regions worldwide, is Fhb1. While investigating Fhb1 candidate genes as part of our ongoing efforts to clone this gene, we discovered that the recipient genotype, ‘Bobwhite’ inhibited the effect of Fhb1. Additionally, in previous studies mapping FHB resistance, resistant loci have been found that were contributed by the susceptible parent. Given these findings, we believe there’s either an inhibitor of Fhb1 present in this background, or a susceptibility factor conferred by ‘Bobwhite.’ To determine the genomic regions causing this susceptibility, we crossed the Fhb1-containing NIL ‘260-2’ to the susceptible line ‘Bobwhite,’ which does not contain Fhb1, and selected all 129 RIL’s that were homozygous positive for Fhb1 to comprise a mapping population. Two seasons of single-floret (point) inoculations in the greenhouse and one conidial spray–inoculated field nursery were used to characterize the reaction of the population. Genotyping is being performed using the 9K SNP Infinium assay. Here we report the QTL identified from the preliminary analysis and postulate whether this response is due to an inhibitor of Fhb1.