A half diallel crosses involving five Egyptian cotton genotypes was used to study the inheritance of seed-cotton yield per plant and lint yield. The analysis of the F₁ generations and parents revealed that both additive and dominance gene effects were important in controlling the variation in the yield traits, but the effects of genes acting additively were more pronounced. The D parameter denoring additive variance was larger than the dominance H₁. Partial dominance was manifested for all studied traits. Narrow sense heritability was high for flowering time (0.81), seed-cotton yield (0.87) and lint yield (0.83) but low for lint percentage (0.18).