A full diallel cross involving four indigenous and four exotic genotypes was used to study the inheritance of oil content in seed of Gossypium hirsutum L. Data from F1 generation and parents were analysed using Hayman-Jinks method of diallel analysis. Both additive and dominance effects appeared to be important for controlling the variation in oil content, but the effects of genes acting additively were more pronounced with varying degree of dominance. The dominance acted in the direction of parents having high content of oil. Estimate of heritability in narrow sense was 95%. The additive gene action and the high heritability suggest that rapid improvement in oil content is possible in this species by making straightforward selection of plants in the F1 population