We have developed an expanded system (RLGS Ver.1.8) for producing RLGS patterns that result in a 16-fold increase in the number of gels produced and a 10-fold reduction in the total cost per gel. The major modifications include: 1) performing the blocking and labeling step without phenol extraction or ethanol precipitation; 2) minimizing the reaction volume and the enzyme units in each step; 3) developing a long vertical agarose disc gel electrophoresis for the 1st-dimension; and 4) developing a new apparatus for multiplex vertical 2nd-dimensional electrophoresis. RLGS Ver.1.8 was used with a new combination of restriction enzymes to identify variation for 209 loci between C57BL/6J and DBA/2J. Twenty-six BXD RI strains were analyzed and 195/209 loci were genetically mapped. These loci were mapped in one week of laboratory work by two people. This system provides an important tool for the genetic analysis of new loci in similar genetic resources.