Small cortical suction ablations were produced at one of several stereotaxically located sites along the anterior-posterior axis of the right or left hemisphere in the rat. Analysis of variance showed a highly significant effect of lesion location in the right hemisphere on locomotor activity. The most anterior lesions produced both the most hyperactivity and also the greatest reductions in the concentrations of norepinephrine in the ipsilateral and contralateral cortex and locus coeruleus. These results suggest that the effect of cortical lesions on spontaneous activity may be graded across the right hemisphere and that the anatomy of certain neurotransmitter pathways in the cortex may help to explain both the biochemical and behavioral findings.