This chapter focuses on the breeding systems of Neotomine-Peromyscine rodents. There are three specific objectives to this chapter. First, we describe the patterns for major Neotomine-Peromyscine clades using data collected from the literature (table 6.1). Second, we examine data from the literature on the following breeding behaviors: male spacing, female spacing, relative intersexual home range/territory size, paternal care, and juvenile dispersal patterns. We examine breeding behavior data in a phylogenetic framework to test if any phylogenetic patterns emerge in the observed variation in these breeding behaviors and if relationships occur among these behaviors. Third, we examine in a phylogenetic framework whether dietary, physiological, or life-history characteristics of the taxa are able to explain the observed variation in these breeding behaviors.