The recessive male sterility and histoincompatibility (mshi) mutation in the mouse generates pleiotropic effects on histocompatibility and male reproduction, while female mutants appear to be reproductively normal. We have mapped the mshi mutation to mouse Chromosome (Chr) 10 by analysis of 126 progeny from an intraspecific backcross. Our analysis both places the male sterility and histoincompatibility controlled by mshi within a 20-cM interval between the markers D10Mit51/D10Mit212 and D10Mit170 and has allowed the ordering of several other microsatellite markers on Chr 10 that were previously unresolved. The high-resolution backcross panel we describe should facilitate the isolation of more tightly linked probe sequences and, ultimately, the molecular identification of the gene or genes affected by this interesting mutation.