The six generation model is considered the best model to estimate additivity of genes and deviation from additivity including epistasis. Thus the present study was carried out at Sids Agricultural Research Station, Wheat Research Department during the three growing seasons 2017/2018, 2018/2019 and 2019/2020. The objectives of this investigation were to estimate the mean performances, gene action, heterosis, inbreeding depression and water deficit stress index under normal and water deficit stress conditions for grain yield and yield components. Six populations (P1, P2, F1, F2, BC1 and BC2) were produced from the two crosses Bani Suef 6 × Bani Suef 3 and Bani Suef 5 × Sohag 4. Six parameters were estimated, namely means (m), additive (a), dominance (d), additive × additive (aa), additive × dominance (ad) and dominance × dominance (dd). The mean effects are highly significant for all studied characters in the two crosses, indicating that these traits are quantitatively inherited. Heritability values in the broad and narrow sense were high and moderate in the two crosses under the normal and the water deficit stress conditions. Meanwhile, inbreeding depression was positive and highly significant for all characters under normal and water deficit stress conditions. In the two crosses, regarding average degree of dominance values, they were more than unity for all characters under study, except for number of spikes plant-1 in the second cross. The results indicated that the two parents involved in the second cross had low sensitivity to water deficit stress, so that most of the generations from the second cross had low values for both tolerance index(TOL) and yield reduction ratio (YR).