The genetic determination of variability of barley doubled haploid (DH) lines in regard of their susceptibility to Fusarium head blight caused by Fusarium culmorum was studied. The susceptibility was evaluated in a 3-year field experiment on the basis of reduction in yield traits and mycotoxin accumulation in infected kernels. The following traits were analysed in inoculated and control plants: kernel number and weight per ear, 1000-kernel weight, percentage of plump kernels (>2.5 mm), deoxynivalenol (DON) content and nivalenol (NIV) content of kernels. On the basis of the obtained data, heritability coefficient (ratio of genotypic to phenotypic variance) was assesed, and genetic parameters as well as the number of effective factors were estimated. Heritability coefficients calculated from two-way analysis of variance, i.e. regarding the influence of years and year ? genotype interaction, appeared to be exceptionally low and ranged from 5.2% for the reduction in plump kernels to 38.2% for the reduction in 1000-kernel weight. In the case of mycotoxin accumulation about 60% of the observed variability in NIV concentration and 30% in DON concentration resulted from genetic differences among lines. Additive effects of genes were important for all the analysed traits. Significant effects of dominance and dominance ? dominance were observed for 1000-kernel weight and percentage of plump kernels. Moreover, it was found that the observed variability in yield trait reduction resulted from the segregation of 5-6 effective factors, DON content from 4 factors, while NIV content from 5 factors.