Djungarian hamsters (Phodopus sungorusi were observed in a series oflaboratory tests, including home cage activity, wheel running, open-field behavior, sexual dimorphism for body mass, copulatory behavior, tonic and dorsal immobility, climbing, digging, nest building, and parental behavior. Fourteen resulting measures were compared with previous results from this laboratory from a variety ofmuroid species. A cluster ofbehavioral adaptations emerged with several marked similarities to the behaviors of a group of North American Microtus species, whereas other behaviors appeared to more closely reflect the classification of the hamsters as cricetines. It is suggested that Phodopus and Microtus species may have evolved many similar adaptive characteristics in response to shared environmental variables.The description and understanding of the behavioral adaptations of organisms are tasks of major importance confronting students of animal behavior. With comparisons of a number of behavior patterns in a variety of species, clusters of behavioral adaptations emerge. These associations of behavioral adaptations, coupled with information regarding the ecological, morphological, and physiological attributes of members of related species, will lead to testable hypotheses concerning the relations among these variables. The resulting general laws may describe a complex of adaptations that are applicable across a wide selection of taxa (Jarman, 1982).Rodents of the superfamily Muroidea are numerous and widely distributed; they inhabit a great range of ecological niches, making them particularly valuable as subjects in comparative research. Most of these species are small, nocturnal, and generally secretive in their habits, making field observations of behavior difficult. However, laboratory investigations can allow direct comparisons of several species in a variety of standardized testing situations. In addition, laboratory tests can be selected that allow behaviors to be quantified easily and data to be collected quickly.Over the past 15 years, muroid rodents have been the subjects of a substantial behavioral research program in this laboratory.