Diallel crosses of seven parents belonging to Gossypium spp. were studied for component of variance analysis for seed cotton yield and fibre traits. Both additive and non additive gene actions were important for seed cotton yield and uniformity ratio. The dominance components (H1 and H2) were significant and greater than additive (D) component indicating major role of dominance gene action. The study also indicated over dominance for all the six traits.Heritability in narrowsense was high for lint index, 2.5% span length and uniformity ratio, while it was low for seed cotton yield, ginning outturn and seed index.