The manifestation of the phenotypic dominance degree of the main stem length in F1 under hybridization of different varieties of bread winter wheat was studied during different for hydrothermal conditions 2018–2020. In the hybridization of Bilotserkivska napivkarlykova variety with medium-growing varieties of groups 1 and 2, the most common type of stem length inheritance was negative overdominance – 54.5 % and positive overdominance – 27.3 %. The degree of phenotypic dominance varied from -63.0 to +7.4. When used medium-sized varieties of group I in the crossing with the maternal form, the degree of phenotypic dominance had a signifcant differentiation from -257.0 to +35.0, and the determination of stem length in most combinations was negatively overdominated – 61.4 %. The combinations Shchedra nyva/Dobirna, Shchedra nyva/Vidrada, Myronivska early/Kolchuga, Antonivka/Vidrada were characterized by a stable manifestation of a negative degree of phenotypic dominance (h p > -1). When involved in the hybridization of medium-sized varieties of group 2 in the maternal form, the most common type of stem length inheritance had negative dominance as well. It was found that the degree of phenotypic dominance of stem length in F 1 depended on the selection of parental forms for hybridization and year conditions. Thus, in 2020, under more favorable conditions for the formation of stem length in most hybrids, a negative degree of phenotypic dominance was determined, and the inheritance was negatively dominated. High rates of negative hypothetical and true heterosis were found in the following hybrids: Shchedra nyva/Dobirna, Shchedra nyva/Vidrada, Kolchuga/Chornyava, Kolchuga/ Antonivka, Yednist/Dobirna, Kolchuga/Vidrada in 2018; Chornyava/Antonivka, Shchedra nyva/Dobirna, Shchedra nyva/Vidrada, Chorniava/Shchedra nyva in 2019; Myronivska early/Antonivka, Zolotokolosa/Antonivka, Myronivska early/Kolchuga, Myronivska early/Vdala, Zolotokolosa/ Yednist, Shchedra nyva/Stolychna, Shchedra nyva/Vidrada, Antonivka/Yednist, Antonivka/Vidrada, Kolchuga/Vidrada, Kolchuga/Stolychna in 2020. Key words: bread winter wheat, crossbreeding combinations, hybrids, main stem length, degree of phenotypic dominance, hypothetical and true heterosis.