Rats with bilateral lesions of the anterior caudate nucleus or the dorsolateral frontal cortex were tested against sham-operated rats in a straight-alley dominance situation. In 91% of encounters the caudate lesion rats forced the sham-operated animals to retreat. The frontal lesion rats won only 56% of their encounters, a proportion no different to that expected by chance. The performance of the caudate-damaged rats could not be explained satisfactorily in terms of increased motivation, changes in activity, motor impairments, or perseverative tendencies. It seemed more likely that the apparent increase in dominance was associated with changes in the level of aggression.