The human DNA probe G8 defines D4S10, a polymorphic locus tightly linked to the Huntington's disease gene on human chromosome 4. A subclone of G8, pSC33, showed significant cross-hybridization to discrete restriction fragments in total genomic mouse DNA. The probe detected restriction fragment length polymorphisms (RFLPs) with the enzymes Taq I and Msp I, permitting chromosomal localization of the mouse G8 homolog by linkage analysis using three sets of recombinant inbred mouse strains: BXH, BXD, and AKXD. The mouse locus was mapped to the central region of chromosome 11 at 1 centiMorgan from the SPARC gene, a locus whose human counterpart is on human chromosome 5.