This study was designed to determine whether CuZn-superoxide dismutase (SOD) is neuroprotective against aging in the nigrostriatal tract. Twenty-four male mice transgenic for human CuZnSOD, resulting in overexpression of the cytosolic enzyme, were compared with 11 matched controls over 19 months. There was no difference in longevity, locomotor activity, or 3H-mazindol or 3H-spiperone binding in the nigrostriatal tract in the two groups. Thus there was no evidence that increased CuZnSOD was neuroprotective in this model.