Abstract: A complete diallel cross experiment involving four cotton genotypes was conducted to ascertain the genetic basis of variation in some fibre traits. Additive type of gene action with partial dominance was observed for fibre fineness, fibre uniformity ratio and fibre elongation whereas over dominance type of gene action was operative for fibre strength and fibre maturity. Non allelic interaction was absent in the inheritance of all these traits. It is suggested that partial dominance with additive gene action for the characters under study, selection would be very useful in the early segregating generation.