Abstract: Two hybridized combinations between four self-lines of parents (Brassica juncea var. tumida Tsen et Lee) with different tumorous stem shape were studied to determine inheritance of tumorous stem shape in their progeny family groups P₁, P₂, F₁, B₁, B₂ and F₂ by joint segregation of major genes plus polygenes. Tumorous stem shape in the cross of y203 × b145 was controlled by two major genes with additive-dominant-epistatic effects. Heritability values of the major gene in B₁, B₂ and F₂ populations were estimated as 59.89%, 26.18% and 54.14%, respectively. Tumorous stem shape in the cross of y92 × b146 was controlled by two major genes with additive-dominant-epistatic effects, plus polygenes with additive-dominant effects. Heritability values of the major gene in B₁, B₂ and F₂ populations were estimated as 22.44%, 58.06% and 63.14%, while those of polygenes were 40.42%, 4.36% and 1.26%, respectively. These results showed that major gene effects were important and should be utilized in breeding programs. The improvement of tumorous stem shape trait should be selected in middle and high generations.