Subcutaneous inoculation of Leishmania mexicana amastigotes into the shaven rumps of DBA/2 mice results in a unique 'no lesion growth' phenotype not observed in other mouse strains. Statistical analysis (Kolmogorov-Smirnov and log likelihood tests) of lesion diameters in F1, F2 and backcross progeny from (C57BL/6 x DBA/2) matings indicate that segregation between lesion growth and no lesion growth phenotypes comes under single gene control. The gene has been designated Scl-2 for susceptibility to cutaneous leishmaniasis locus 2. Preliminary mapping studies using 12 of the 26 BXD recombinant inbred mouse strains suggest a location for Scl-2 near Xmmv-8 on a region of mouse chromosome 4 showing homology with human 9p. The identification and mapping of this murine resistance gene could provide an important tool for genetic analysis of susceptibility and resistance to cutaneous leishmaniasis in man.