Examination of cytochrome-b DNA sequences from specimens of Notiosorex crawfordi, the desert shrew, indicate that within this taxon there are at least 3 major subdivisions reflecting levels of variation more typical of species rather than subspecies. One of these cytochrome-b haplotypes was recently described as a previously unrecognized species; however, that paper was limited to the description of a species level name. We provide additional insight into subdivisions in N. crawfordi. One DNA haplotype is distributed in Texas, New Mexico, and eastern Arizona, a second haplotype in Arizona and Sonora, Mexico, and the third haplotype in Baja California, Mexico. Nucleotide sequences obtained from intron 7 of the nuclear gene, beta fibrinogen, support the conclusions that 2 of the haplotypes occur sympatrically in southeastern Arizona and are not hybridizing with each other.