The main objective of this investigation was to study the effect of Gamma irradiation with a dose of 10 Kr on means, variance, heterosis, inbreeding depression, epistatic effects, genetic variance, heritability estimates and response to selection. Means: In Gamma ray treatment, the means were significantly increased in M2 generation than in the untreated for number of fruiting branches (P1, F1, F2 and B1), number of bolls per plant (P1. F1 and B1), boll weight (P2, F1 and B1), seed cotton yield (P1, P2, F1 and B1), lint percentage (P1, F1 and B1) and fiber strength (B1 and F2). On the other hand, the means were significantly decreased for date of the first flower (P1, F2 and P2) and date of the first open boll , earliness, (P1, F1, F2 and B2). Variance: In gamma irradiation treatment, the variance were significantly increased for date of the first open boll (P1, P2, F2 and B1), position of the first fruiting node (six population), number of fruiting branches (P1, P2 and BC2), number of bolls per plant (P1, P2, F1, F2 and B1), fiber fineness (B2), fiber strength (B1 and B2) and position of the first fruiting node, boll weight, seed cotton yield per plant and plant height (P1, P2, F1, F2, B1 and B2). Heterosis , Inbreeding depression and Epistasis: Gamma ray treatment showed significant and positive heterosis for number of fruiting branches, number of bolls per plant, seed cotton yield per plant, fiber fineness and fiber strength. Inbreeding depression showed positive and significant after gamma ray treatment for plant height and fiber strength. E1 and E2 epistatic effects were significant and positive for date of the first flower, date of the first open boll, meanwhile, E2 was significant and positive for number of the first fruiting node and number of fruiting branches. Genetic variance: Gamma ray treatment showed increased for date of the first flower, date of the first open boll, number of first fruiting node, number of bolls per plant, seed cotton yield per plant, plant height and fiber strength. Heritability Estimates and Response to Selection: Percentages were higher for date of the first flower, number of the first fruiting node, seed cotton yield per plant, fiber fineness and fiber strength as affected by gamma ray treatment.