A distributional and zoogeographical analysis based on published records and approximately 13,000 specimens is provided for the 122 naturally occurring mammalian species in Sonora, Mexico. Twenty-eight species of unverified occurrences which could be present in Sonora are discussed. Domesticated mammals are listed and introduced species are briefly discussed. Descriptions of the topography, climate, vegetation, and hydrological features of Sonora are included. Dichotomous keys provide for the identification of Sonoran mammals to the level of order, family, and species. Species accounts include the following: scientific and common names, additional identification remarks, general distributional discussions, various ecological and biological remarks, records of known occurrence, and distributional range maps.

Distributional patterns are discussed ecologically and geographically. Eighteen physiognomically described community types are defined. Similarities in mammalian composition among community types are compared using a phenogram constructed by the Unweighted Pair-Group Method using Arithmetic averages (UPGMA) clustering process. The similiarity values clustered were Jaccard's Coefficient of Communities which were calculated between each community type. The clustering process suggested three main ecological complexes of mammals in Sonora: a subtropical group, a mid-to-upper elevation group, and a lower elevation group.

A computer-constructed species density contour map indicated the number of species across Sonora varied between 54 and 95 species. Superimposed species range limits and analysis (UPGMA cluster analysis of distance dissimilarity coefficients) of presence-absence data of species in a grid system suggested five different mammalian provinces in Sonora: Sonoran, Trans Sonoran, Sinaloan, Yaquian, and Upper Mapimian. Faunal element analysis suggested at least five faunal units (Chihuahuan, Yuman, Neotropical, Campestrian, and Eastern) contribute species elements to the total fauna of Sonora.