Abstract: Grain dimension is one of importantly agronomic traits in rice, which can affect the yield, the processing habit of grain and the market value of rice. This study was conducted to identify Quantitative Trait Loci (QTLs) for Grain Length (GL), Grain Width (GW) and grain Length-width Ratio (LWR), which mainly represent grain dimension in rice, using recombinant inbred (RI) population derived from a cross between a japonica variety, Asominori and an indica variety, IR24, grown in Japan (2002) and China (2005). Continuous distributions and transgressive segregations of GL, GW and LWR in rice were observed in the RI population, suggesting that grain dimension was quantitatively inherited trait. A total of ten QTLs for grain dimension were mapped to chromosomes 1, 2, 3, 5, 7, which explained 7.0~36.6% of total phenotypic variation and five out of them were commonly detected in the both countries. The results and the tightly linked molecular markers that flank the five common QTLs will be useful in rice-breeding for grain dimension improvement in Asian countries.