Dormancy indices of hulled and dehulled seeds were investigated by using 19 cytoplasmic male sterile (CMS) lines, 9 restorer lines and their 109 F1 hybrids of indica hybrid rice. The seeds of each F1 and the parents were harvested on 35 days after flowering. Combining ability was analyzed in 25 combinations made by 5 CMS lines and 5 restorer lines (North Carolina II mating design). The seed dormancy index of F1 was positively and highly significantly correlated with those of their parents and mid-parent value. Out of the 109 combinations, 82 combinations showed mid-parent heterosis, and 43 heterobeltiosis. Seed dormancy indices of F1s and their parents declined dramatically in dehulled seeds compared with hulled seeds, indicating that the hull played an important role in seed dormancy. However, the trends were similar in hulled seeds and dehulled seeds in terms of relationships between the seed dormancy indicices in F1 and their parents. The influence of hull on seed dormancy mainly depended on F1 genotype, not on the hull from maternal parent. The variances of general combining ability (GCA) in female and male parents occupied 59.2% and 31.1% of total variance, respectively. The variance of specific combining ability (SCA) in combinations occupied 9.7% of total variance, indicating that gene additive effects were principal. Among the 5 CMS lines, II112A had the highest GCA effect for seed dormancy, followed by D62A. Among the 5 restorer lines, IR112 had the highest GCA effect for seed dormancy, followed by 2786. These lines are elite parental materials for breeding F1 hybrid rice with stronger seed dormancy. Dormancy indices of hulled and dehulled seeds were investigated by using 19 cytoplasmic male sterile (CMS) lines, 9 restorer lines and their 109 F1 hybrids of indica hybrid rice. The seeds of each F1 and the parents were harvested on 35 days after flowering. The seed dormancy index of F1 was positively and highly significantly correlated with those of their parents and mid-parent value. Out of the 109 combinations, 82 combinations showed mid-parent heterosis, and 43 heterobeltiosis. Seed dormancy indices of F1s and their parents ago dramatically in dehulled seeds compared with hulled seeds, indicating that the hull played an important role in seed dormancy. However, the same were similar in hulled seeds and dehulled seeds in terms of relationships between the seed dormancy indicices in F1 and their parents. The influence of hull on seed dormancy mainly de The variances of general combining ability (GCA) in female and male parents 59.2% and 31.1% of total variance, respectively. The variance of specific combining ability (SCA) in combinations Among the 5 restorer lines, IR112 had the highest GCA effect for seed dormancy, followed by D62A. Among the 5 restorer lines, IR112 had the highest GCA effect for seed dormancy, , followed by 2786. These lines are elite parental materials for breeding F1 hybrid rice with stronger seed dormancy.