Genetical architecture of yield per plant as well as yield compo­nent (rails in flax (Linum usitatissimum L.) from F1 and F2 data of a 6 x 6 diallel cross using Hayman's method was investigated during the period from 1999 to 2002. Mean squares due to genotypes were significant for all traits except number of basal branches per plant in both F1 and F2 generations. Estimates of the average degree of dominance (H1/D)¹¹² re­vealed that over dominance or epistasis is important in the inheritance of yield per plant and yield component characters in both generations ex­cept seed yield per plant and 1000-seed weight in Fl, where partial dominance was detected. Concerning gene distribution, positive and neg­ative genes exhibiting dominance were unequally distributed among the parents in most cases. The results showed that at least one group of genes is involved in controlling yield per plant and yield component char­acters. Heritability estimates (narrow sense) were low for biological yield, straw yield and number of capsules per plant: moderate for seed per plant and number of seeds/capsules: whereas high heritability esti­mates were obtained for plant height and 1000-seed weight, revealing that additive genes had a major role in the inheritance of such traits and that improvements could be done through selection programs. Graphical analysis showed that the parent $.2465/1 contains dominant genes for biological yield per plant and plant height. The parent Giza8 appeared to possess dominant genes for plant height, whereas the parent Giza7 ap­peared to contain recessive genes for the same trait. The results showed clearly that accumulation of recessive genes induce maximization for seed yield per plant as well as plant height and technical stem length.