Fusarium head blight (FHB) is one of the most devastating diseases of barley. FHB is caused by a species complex of Fusaria, of which Fusarium graminearum is the species responsible for most FHB epidemics in Canada. Field surveys show that two or more Fusarium species often co-exist within the same field or grain sample and F. poae is reported as another dominant species in barley in eastern Canada. The aim of this study was to determine the pathogenicity of F. graminearum, F. poae and a co-inoculation of both species causing FHB in barley under controlled conditions. Two susceptible barley genotypes were spray-inoculated at 10 to 14 days after heading. Phenotypic disease severity was rated on a scale of 0-9 at 4, 7, 14, and 21 days after inoculation. There was a significant difference in FHB severity between F. graminearum and F. poae, where F. graminearum produced more severe disease ratings. F. poae was less pathogenic and not statistically different from the control treatment (inoculated with deionized water only). When heads were co-inoculated with both Fusarium species, the resulting FHB severity was lower than that caused by F. graminearum alone. This suggests that the presence of F. poae may reduce the pathogenicity of F. graminearum in causing FHB, however according to our preliminary data, this difference is not significant.