The construction of a genetic linkage map is the first, fundamental step to analyze the genetic properties of any organism. For this purpose, the restriction landmark genome scanning method (RLGS) can be used and has been shown to have high productivity in various genetic analyses. However, construction of a genetic linkage map by the RLGS method is laborious, because hundreds of spots must be scored, usually by visual observation. In order to reduce human involvement in the data processing, we developed an image analysis software, RAT (RLGS Analysis Tool). We evaluated its accuracy and feasibility by comparing the parental distribution patterns of RLGS spots obtained by RAT and by human observation, using Syrian hamster strain backcross progeny. We then used RAT to construct a genetic linkage map of the recombinant inbred strain SMXA. We were able to obtain 121 progenitor strain-specific spots that were assigned to a specific chromosome.