This study attempts to demonstrate the possible role of agonistic behavior and vocalization in maintaining the spatial organization found in a population of 12 eastern chipmunks, Tamias striatus. The home ranges of the chipmunks overlapped almost entirely, but their burrow entrances were regularly spaced in the study area and their core areas did not overlap. Agonistic behavior was studied while attracting the chipmunks to small piles of sunflower seeds. Chasing occurred most often in 398 agonistic encounters. The chase orders at 15 locations in the study area were remarkably different. Reversal of dominance consistently occurred between neighboring chipmunks. Each chipmunk seemed to maintain a dominance area centered around its burrow entrance. This dominance area roughly coincided with its core area. If reversal of dominance with difference in space is accepted as a criterion of territorial behavior, chipmunks seem to exhibit territorial behavior. Chipmunk vocalizations form a graded sound system. There is a gradation of both temporal patterning and frequency. All vocalizations seem to function as alarm calls. One of the vocalizations, chipping, may also function as an agonistic signal. Reciprocal chasing between neighboring chipmunks may in part explain the regular spacing of burrow entrances and the mutual exclusiveness of the core areas. Since each animal's dominance area centers around its burrow entrance, the chipmunk can, by chasing, prevent another chipmunk, from digging or using a burrow near its own. Since the dominance area roughly coincides with its core area, the animal can likewise prevent other chipmunks from frequenctly using its core area. It is also possible that the vocalizations of the chipmunks, especially chipping, help maintain the spatial organization of the population. The chipping could well advertise the presence of a chipmunk in its dominance area, thereby dissuading intrusion by neighboring chipmunks.