Immature embryos of 99 varieties of barley were cultured to investigate the ability of callus growth and plant regeneration. These two in vitro traits showed wide and continuous variations among the barley varieties tested. Ability of callus growth, which were evaluated by callus diameter ranged from 3.9mm to 11.2mm, and ability of plant regeneration from the calli ranged from 0% to 100%. A set of complete diallel crosses was made using six cultivars as the parents which differed in ability of callus growth and plant regeneration. The Vr/Wr graphical analysis showed that there were epistasis, or interaction among nonallelic genes for callus growth. As to ability of plant regeneration, no epistasis existed in the subdiallel without P1 (J232) which showed high specific combining ability, and it was controlled by a simple additive dominance genetic system. The mean degree of dominance(0.42) was relatively low and the broad(0.86) and narrow(0.78) sense heritabilities were high.