Studies were carried out to investigate the mode of gene action governing the inheritance of geedcotton yield, lint yield, lint percent, mean fiber length and fiber fineness within six intervarietal crosses of Upland cotton. Polygenic inheritance for these characters was indicated by unimodality in the F2 distribution in most of the crosses for the traits studied. There were also apparent indications of the presence of complementary effects of genes for all these traits except lint yield as shown by skewness of some of the F2 distribution. The fit method of comparing the average of different generations with a predicted average calculated from parental and F1 means was used to determine gene action in the inheritance. Results showed that this method was not sufficiently discriminatory as a means of studying the mode of gene action with respect to the traits evaluated using the available data. However from visual observation of the F2 distribution, heterosis pattern and heritability estimates, additive gene effects appear to be relatively more important than non-additive effects in the inheritance of seedcotton yield, lint yield, lint percent and mean fiber length while dominance gene effects seem to be more important than additive effects in the inheritance of fiber fineness There is also an indication of over-dominance at the coarse level for this character in three out of the six crosses evaluated.
