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Peromyscus eva and Peromyscus fraterculus are 2 morphologically similar species of the Peromyscus eremicus group occurring on the Baja California Peninsula Due to the similarity between these 2 species their ranges have been greatly confused consequently) the specific habit it characteristics for etch group ire not well known The goal of this study was to assess distribution ranges and characteristics of prefered habitats for P eva and P fraterculus in more detail We identified taxonomy of individuals by evaluating genetic patterns produced by restriction fragment length polymorphisms (RFLPs) We evaluated the binding pattern generated by Alu I and Bam H1 restriction enzymes in an 850 bp cytochrome b fragment Consistent differences in number and size of fragments allowed for discrimination of individuals to species the heterogeneity and evenness Indexes showed that the microhabitat it of P fraterculus con tamed less diverse soil types and is mote homogeneous than the microhaibitat of P eva In the state of Baja California Sur P eva occurs exclusively in the flat areas along the Pacific coast from the Vizeamo Desert to the south including Margarita Island with one small population in the Loreto area adjacent to Carmen Island The habitats occupied by P eva were heterogeneous (areas with friable soft sandy soil and a slow percentage of sin ill stones) Peromyscus fraterculus occurs mostly in Baja California Norte with some populations distributed in Baja California Sur particularly in the western areas of the Vizeamo Desert along the mount no range in the gulf side of the penmsula a south of the city of La Paz and in a small area on the eastern side of Sierra de Las Cruces This species was mostly found on haul soil with high medium size stone content