An indica rice cultivar, Milyang23 is a semidwarf plant type with long and slender grains, whereas a temperate japonica rice cultivar, Stejaree45 is a japonica cultivar with short and bold grains. Genetic analysis was carried out to determine the number of quantitative trait loci (QTL), chromosome location, gene action, and effects of QTLS controlling grain length, width, thickness, and shape. The grain traits averages in the recombinant inbred lines (RILs) were near the mid-parent value, but the standard deviations in the RILs were more than those of the parents. A linkage map based on 138 simple sequence repeat (SSR) markers from 12 linkage groups was constructed using the 143 RILs as the base population. The map, spanning 1208 cM of the rice genome with an average interval length of 12.9 cM, was used for QTL analysis. A total of 13 QTLS for grain quality traits were identified. The phenotypic variation accounted for by each QTL ranged from 4.2% to 10.4%, with an average of 6.7%. Among the 13 QTLS, only one QTL accounted for more than 10% of the total phenotypic variation. Each of the traits studied was governed by one or two major QTLs that accounted for the large proportion of the total phenotypic variation. Several minor QTLS explain a small proportion of the total phenotypic variance.