Injections of [14C]-deoxyglucose ([14C]DG) were used to study rates of local cerebral glucose utilization (LCGU) in control cats and cats subjected to concussive brain injury produced by a fluid-percussion device. Studies in separate groups of animals demonstrated that the injury level selected produced transient behavioral suppression probably associated with traumatic disturbances of consciousness. LCGU was sampled near the site of fluid-percussion injury and more caudally in pontine regions. Histopathologic studies examined the possibility of hemorrhage, contusion, or breakdown of the blood-brain barrier in regions within which LCGU was calculated. These studies yielded analyses indicating that (1) the [14C]DG technique can be applied usefully to infer changes in regional levels of brain activity after concussion, (2) concussive injury produces changes in brain function that differ reliably across various regions of the central nervous system and may include both depression and focal activation of specific brain sites. Data are discussed that suggest that changes in brain activity in specific regions indicated by changes in LCGU could contribute to acute neurologic disturbances after concussion including unconsciousness.