The locus responsible for resistance to the anticoagulants warfarin and bromadiolone (locus symbol Rw) was integrated into the rat (Rattus norvegicus) microsatellite genome map. Seventh-generation offspring of a segregating strain of rats heterozygous resistant to both compounds were tested with a blood-clotting-response (BCR) test. No recombination between resistance to warfarin and bromadiolone was observed, indicating a common genetic basis. No recombinants were found between Rw and D1Arb18 (Myl2) located at the MIT-microsatellite map position 95.90 (SHRSP x BN F2-cross) or 82.24 (FHH x ACI F2-cross). Resistance segregated in a ratio expected for single, dominant gene responses. An equal number of females and males were resistant, but females retained higher percentage blood coagulation activities (PCA) after anticoagulant administration. Partial synteny between rat, mouse, and human suggests that Myl2 may serve as anchor to map the Rw homologs in mouse and human.