This investigation was carried out at Bahteem Agric. Res. Station through the three growing seasons of 2005/2006, 2006/2007 and 2007/2008 aiming to study gene effects for yield and its components in four bread wheat crosses namely; 1-(Gemmeiza 9 X Giza 168); 2- (Sids 1 X Giza168); 3- (Sids 1 X Sakha 8) and 4- (Sakha 8 X Gemmeiza 9). The results showed that additive gene effects (d) was important in the inheritance of spike grain weight, number of grains/spike and kernel weight in the 1^st cross. Meanwhile, dominance genetic variance was the main components controlling the inheritance of plant height, spike grain weight, number of grains/spike and kernel weight mainly in other crosses. The results of the two digenic epistatic effects additive X additive (i) and dominance X dominance (L) confirm its importance role in the genetic system controlling most of the studied characters. Over-dominance cases were involved in the inheritance of plant height, spike grain weight, number of grains/spike and 100-kernel weight in the 1^st cross, while partial dominance was present for both number of spikes/plant and total weight/plant in the same cross. The 4^th cross gave the highest heterotic value over its better parent for grain yield/plant followed by the 3^rd cross and at the same time gave highly heterotic values for at least one of its yield components for number of grains/spike. The highest estimates of narrow sense heritability were detected for plant height, grain yield/plant, kernel weight and number of grains/spike in the 1^st cross. Moderate heritability estimates were also detected for total weight/plant in the 1^st and 2^nd crosses. High expected genetic gain were found to be associated with high narrow sense heritability estimates which makes selection for such traits in the early generations possible