Photoperiod-sensitive genic male sterile (PSGMS) rice is a very useful germplasm for hybrid rice development. It was first found as a spontaneous mutant in a japonica cultivar ’Nongken 58.pms3 on chromosome 12 was determined to be the locus where the original PSGMS mutation occurred, changing the normal cultivar Nongken 58 to PS-GMS Nongken 58S. Large amounts of RAPD and AFLP analyses were also conducted for the fine mapping of the pms3 genomic region, which resulted in 4 molecular markers linked to pms3. Although these markers somewhat increased the marker density of this region, the pms3 locus is still located in a marker-sparse region.