Agonistic behavior of heteromyid rodents has been studied using staged encounters in the laboratory, but there have been no previous attempts to test for a linear dominance hierarchy among individuals of the same species. Dominance hierarchies are important in learning about sociality, priority of access to resources and consequences for individual variation in fitness. We used standard laboratory methods to assess agonistic behavior of Merriam's kangaroo rats, Dipodomys merriami. Males exhibited a dominance hierarchy that was strongly linear. Dominance rank was not correlated with body mass, but dominant males lost greater percentages of their body mass during trials than did subordinate males. Males dominated females and females showed little agonistic behavior in intrasexual trials. The linear dominance hierarchy among males may have reflected individual variation in aggressive tendencies, but dominance rank was not correlated with individual variation in total amounts stored or proportions of seeds larderhoarded in food-hoarding trials. Different patterns of individual variation in males and females are promising topics for future research.