Abstract: Diallel cross analysis experiment of eight varieties/strains of Upland cotton Gossypium hirsutum L. viz: CYTO 9/91, B-496, SLS-1, Niab-78, NIAB-313/12, B-622, NIAB-92 and CYTO-11/9 was conducted at experimental area of the Department of Plant Breeding and Genetics, Faculty of Agriculture, Gomal University, Dera Ismail Khan, Pakistan, during the years 1996-1998 to conclude the combining ability analysis in the inheritance of some quantitative characters like, seeds boll-1, seed index, lint index and staple length using Griffing’s (1956) Method-1, Model-II in F1 generation. The mean squares for General combining ability (GCA), Specific combining ability (SCA) and reciprocals effects were observed to be highly significant for characters of seeds boll-1, seed index, lint index and staple length. The estimates of components of variance exposed that the variance due to SCA was much higher in magnitude and more vital than GCA in case of seed index, lint index and staple length showing thus the prevalence of non additive type of gene action with (dominance or epistatic effects) in the inheritance of the characters mentioned. Concurrently GCA was much higher in magnitude and more significant than SCA in case of seeds boll-1 reflecting the role of additive type of gene action.