The knowledge of gene action would be of great importance to plant breeders as it provides information about possible Improvement of different yield, yield components and fiber properties traits. Hence, this investigation has been done to partition the genetic variance to its components through studies on different generations of two cotton crosses i.e. Giza 89 x Suvin and Gin 86 x Karshenky at Salcha Agricultural Station, during four successive growing seasons (2003-2006). The results showed presence of significants differences among generations in the two crosses for all studied traits. Since, the parents Suvin and Giza 86 have transmitted their performances into their offspring, it could utilize these parents in cotton breeding program for improving these traits. Highly significant positive heterosis was observed relative to mid-parents for most studied traits. In addition, heterosis relative to the better parent was significantly positive, for boll weight, lint cotton yield/plant, lint percentage and 2.5% span length in cross I and for all studied traits In cross II except number of bolls/ plant and fiber strength. Highly significant positive inbreeding depression values were recorded in values F2 and F1 for boll weight, seed cotton yield /plant, lint cotton yield /plant and 2.5% span length in the two crosses is well as, lint percentage, number of bolls /plant and fiber fineness in ucn I and seed index in cross II. Over dominance appeared to be controlling most studied traits in F₁ hybrids and F2 generations in the two crosses and the other remaining traits were controlled by partial dominance. Results of scaling test (C and 0) suggested the presence of non-allelic interaction for boll weight, seed index, lint index, fiber strength and fiber fineness in the crosses indicating that the epistasis effects plays important role in the inheritance of these traits, while number of bolls /plant was the least affected trait. The additive gene effects were positively significant or highly significanu . for 2 5% span length and fiber strength in the two crosses and almost studied trait in CroSs 11 except for lint index. While, dominance effects were positive and highly significant for boa weight, seed cotton yield /plant, lint cotton yield /plant and number of bolls /plant in cross I only and fiber fineness in cross II. Among the epistatic components, the dominance x dominance component (L) was quite positive highly significant and greater in magnitude than additive or dominance components for most studied traits In the two crosses.