MyoD1 alleles distinguish between the Mm musculus and Mm domesticus subspecies of Mus musculus. SJL/J mice, which belong to the Mm musculus subspecies, are able to regenerate skeletal muscle more efficiently than BALB/c mice which possess the Mm domesticus MyoD1 allele. Hence the possibility that regeneration responses are due to species-specific genetic differences including MyoD1 was investigated in this study. Quantitative morphometric analysis following muscle crush injury of 2 Mm musculus strains, MBK and MGL, has indicated that regeneration phenotype is not species-specific and may not be directly related to MyoD1 alleles. These results contrast with prior investigations conducted in SJL/J and BALB/c mice, and indicate that other genes may have a direct influence on skeletal muscle regeneration.