In the present studies the effects of kainic acid (KA)- or quinolinic acid (QA)-induced striatal lesions were compared in different behavioral tests in rats. Both KA- and QA-lesioned animals had ipsilateral barrel-rotation (BR). The KA-lesioned rats, however, had contralateral, while the QA-lesioned rats had both ipsi- and contralateral turning activity. The KA-lesioned animals showed increased open-field activity as well as increased percentage of entries, and time spent in the open arms of Montgomery's conflict test. Learning of an active avoidance response was strongly inhibited by both striatal QA- or KA-induced striatal lesions. The QA-lesioned animals showed less pronounced behavioral changes than KA-lesioned animals in most of the tests, and had a smaller loss of body weight. There was no significant difference in the extent of the KA- and QA-induced substance P (SP) and GABA depletions in striatum, however, the depletions with QA lesions were slightly greater. These findings show that KA-induced striatal lesions produce more pronounced behavioral effects than QA lesions of similar size. It is possible that the differential effects of KA versus QA on striatal interneurons may result in its more marked behavioral effects.