Deer mice (Peromyscus) are the most common native North American mammals, and exhibit great natural genetic variation. Wild-derived stocks from a number of populations are available from the Peromyscus Genetic Stock Center (PGSC). The PGSC also houses a number of natural variants and mutants (many of which appear to differ from Mus). These include metabolic, coat-color/pattern, neurological, and other morphological variants/mutants. Nearly all these mutants are on a common genetic background, the Peromyscus maniculatus BW stock. Peromyscus are also superior behavior models in areas such as repetitive behavior and pair-bonding effects, as multiple species are monogamous. While Peromyscus development generally resembles that of Mus and Rattus, prenatal stages have not been as thoroughly studied, and there appear to be intriguing differences (e.g., longer time spent at the two-cell stage). Development is greatly perturbed in crosses between P. maniculatus (BW) and Peromyscus polionotus (PO). BW females crossed to PO males produce growth-restricted, but otherwise healthy, fertile offspring which allows for genetic analyses of the many traits that differ between these two species. PO females crossed to BW males produce overgrown but severely dysmorphic conceptuses that rarely survive to late gestation. There are likely many more uses for these animals as developmental models than we have described here. Peromyscus models can now be more fully exploited due to the emerging genetic (full linkage map), genomic (genomes of four stocks have been sequenced) and reproductive resources.