C57Bl/6J mice, representing four divergent age groups (ranging from 3 months to 31 months) were each tested on a number of behavioral procedures, selected to sample a wide spectrum of behaviors. The evaluation demonstrated that, as with other mammalian species, not all behaviors in the mouse are affected by old age. Most severely impaired was retention of a single-trial passive avoidance task, most probably reflecting a deficit in memory ability. One tests of motor function, the most demanding tasks revealed the greatest debilitating effects of age, paralleling the effects of task difficulty previously reported in numerous learning studies. Finally, a deficit in the ability to modify preexisting habits in a T-maze learning situation was observed, corroborating reports of increased perseveration in aged humans and nonhuman primates. The similarity of these results across the life span of the C57 mouse with those previously reported for other aged mammalian species demonstrates that certain common types of behaviors seem to be impaired selectively by increased age across mammalian species and raises the possibility that common neurological etiologies may exist for these behavioral deficits.