ABSTRACT Six populations P₁, P₂, F₁, F₂, Bc₁ and Bc₂ of three bread wheat crosses. namely,1) Sakha 95 x Salah-1, 2) Sakha 95 x Rama- 2 and 3) Amna- 2 x Damara- 6, were raised in randomized complete block design during the three successive seasons of  2015 / 2016, 2016/2017 and 2017/2018 at Ismailia Agricultural Research station, El-Ismailia Governorate, Egypt. The six populations were evaluated in two adiacent expirments, one with irrigated by sprinkler system every week throught the season (normal condition) and the other was irrigated by sprinkler system every three weeks throughout the season (drought stress condition). The study aimed to determine the adeguacy of genetic model and gene action controlling days to heading, days to maturity, plant height, No. of spiks / plant, No. of grains/spike, 100-grain weight and grain yield/plant. Results indicated that, drought stress caused significant reductions in all studied traits. The heterotic effect was significant in most cases with a few exceptions. Genetic system and gene expression differed greatly from the normal and drought stress conditions in most cases. Scaling tests (A, B and C) provide evidence for the suitability of simple additive – dominance genetic model for explaining the inheritance of 100-grain weight in 2^nd cross under normal condition and plant height in the 1^st cross, No. of spikes / plant in the 3^rd cross as well as 100-grain weight in the 2^nd cross under drought condition. Otherwise, the complex genetic model was responsible for the inheritance of grain yield/plant, days to heading, days to maturity and No. of grains / spike in all studied crosses under both conditions, plant height and No. of spikes / plant in 1^st, 2^nd and 3^rd crosses under normal condition, also it responsible for plant height in the 2^nd  and 3^rd crosses and 100-grain weigh in the 1^st and 3^rd crosses under normal condition, plant height in 2^nd crosses as well as 100-grain weight in the 1^st and 3^rd ones under drought stress condition. Additive gene effect (d) was significant for days to heading, days to matunity plant height and No. of spikes / plant in all studied crosses and No of grains/spike in 3^rd cross, grain yield / plant in 1^st cross as well as 100-grain weigh in the 2^nd one under normal condition and days to heading and days to matunty in 1^st and 2^nd crosses / plant height in all crosses, No. of spike / plant in 3^rd crosses, No. of grains / spike in 2^nd cross as well as grain yield / plant in 1^st and 2^nd crosses under drought conditions. Both additive (d), dominance (h) and their interaction types, additive x additive (i) and dominance x domiuance (j) were involved in the genetics of days to heading in 3^rd cross and days to maturity and plant height in 2^nd cross under normal condition as well as days to heading in 1^nd cross under drought stress condition. Addilive (d), dominance (h), additive x additive (i), additive x dominance (i) and dominauce x dominance (I) were involved in controlling days to heading in 2^nd cross under drought stress conidian only. Additive (D) genetic variance was important in the genetics of No. of spikes / plant in 3^rd cross and grain yield / plant in 1^st and 2^nd cross under normal condition as well as 100-grain weight in all studied crosses under drought stress condition. The dominance (H) genetic variance was found to be the prevailent type controlling the most remaining crosses under both conditions. Heritability in narrow sense (Tn) was low to moderate percent for days to heading, days to maturity, No. of spikes/plant, No. of grains/spike, 100-grain weight and grain yield/plant in most cases under both conditions.