Flunitrazepam effects on local cerebral glucose utilization in the rat brain were investigated with the (14C) 2-Deoxy-D-Glucose procedure. The drug decreased glucose utilization in many areas of the rat brain, whereas no increases were observed. In this respect, the metabolic effects of flunitrazepam were different from those of other CNS "depressant" drugs, such as isoflurane and phencyclidine. Compared to the metabolic changes induced by diazepam, flunitrazepam peak effects appeared later and involved a greater number of regions.