Staining the brain for cytochrome oxidase (CO) produces patterns which can resemble the patterns produced by 2-deoxyglucose (2-DG) autoradiography. In order to assess the differences between CO patterns of long-term metabolic activity and 2-DG patterns of short-term activity, comparisons should, ideally, be made on the same section. Consequently, we have made certain modifications in the standard CO histologic procedure which improve the stain and allow both 2-DG autoradiography and CO staining on the same section.