Using a population of recombinant inbred lines of the 164 genotypes derived from a cross between ÔMilyang 23Õ (indica) and ÔGihobyeoÕ (japonica) in rice (Oryza sativa L.), salt tolerance was evaluated at a young seedling stage in concentrations of 0.5% and 0.7% NaCl. Mapping quantitative trait loci (QTLs) related to salt tolerance was carried out by interval mapping using Qgene 3.0. Two QTLs (qST1 and qST3) conferring salt tolerance at young seedling stage were mapped on chromosome 1 and 3, respectively, and explained 35.5-36.9% of the total phenotypic variation in 0.5% and 0.7% NaCl. The favourable allele of qST1 was contributed by ÔGihobyeoÕ, and that of qST3 by ÔMilyang 23Õ. The results obtained in 0.5% and 0.7% NaCl for 2 years were similar in flanked markers and phenotypic variation.