Hayman's diallel cross analysis was employed to investigate the nature of genetic system controlling fiber to seed attachment force, fuzz index and fiber quality index characters in Egyptian cotton. Nine parent and their half diallel crosses were grown in randomized complete block design with two replication Heterosis was measured as departure of the F1 from the average mid parent value. The heterosis effects were small for fiber — to seed attachment force and fuzz index. While fiber quality index exhibited sig-nificant effects. The epistasis of non-allelic interaction was absence for all characters. The information were obtained with regard to D and H1 suggest‌ed that in all traits the additive part of the genetic variance was more important than dominance. Concerning gene distribution, the two traits of fiber — to seed attachment force and fiber quality index exhibited equal distribution, while fuzz index exhibited unequal gene distribution. Dominance degree was partial for fuzz index and fiber quality index. While it was complete dominance for fiber to — seed attachment force. Narrow sense heritabilities were 62. %, 90.45% and 62. % For fi-ber — to- seed attachment force, fuzz index and fiber quality index re-spectively. The result obtained from distribution of parent along and / or around the regression line suggested that Giza 84, Giza 77 and Gin 85 were the best parents for breeding program for these traits.