The present work aimed mainly at analysis of gene effects using means of the six populations, P1, P2, F1, F2, BC1 and BC2 for ten characters in two crosses namely cross I (Giza 96 x 10229) and cross II (Giza 89 x 10229). The experiment was grown in a randomized complete blocks design with four replications at Sakha Agricultural Research Station, Kafr El-Shiekh, Egypt. The mean values F1 population was better than the respective parents, F2, BC1 and BC2 populations for most of the traits studied for the two crosses. Highly significant and positive (desirable) heterosis relative to mid- and better-parents for most traits studied was found in the two crosses. On the other hand, the heterosis relative to mid- and better-parent was highly significant and negative (useful) for micronaire reading of the two crosses. Inbreeding depression was highly significant and positive for all traits studied in the two crosses, except number of bolls/plant in the two crosses and micronaire reading in cross II (Giza 89 x 10229) which exhibited highly significant and negative inbreeding depression.The values of phenotypic coefficient of variation (PCV) were higher than the values of genotypic coefficient of variation (GCV) for all the traits studied of the two crosses. Six parameters gene effects exhibited that the dominance gene effect, were higher than additive gene effects for all traits studied in the two crosses, indicating predominant role of dominant component of gene action in inheritance of these traits. High heritability in broad-sense estimates (>50%) were detected for all the traits studied at the two crosses except seed cotton yield/plant at cross II (Giza 89 x 10229) and boll weight of cross I (Giza 96 x 10229). The heritability in narrow-sense estimates ranged from 3.29% to 35.70% for boll weight and uniformity index of cross I (Giza 96 x 10229), respectively. The expected genetic advance (Δg%) under 10% selection of the individual plants in the F2 generation ranged from 10.37% to 92.28% for uniformity index of cross II (Giza 89 x 10229) and lint cotton yield/plant of cross I (Giza 96 x 10229), respectively.