Following cerebral concussion, in which there is no evidence of direct morphological damage, cells are exposed to an increase in extracellular potassium as well as an accumulation of calcium. This concussion-induced ionic flux most likely alters the cellular energy demands thereby modifying metabolic processes. To investigate the metabolic changes after cerebral concussion, local cerebral metabolic rates for glucose (lCMRglc) utilizing [14C]2-deoxy-D-glucose were studied in rats (n = 98; 250-300 g) immediately, 30 min, 6 h, 1, 2, 3, 5 and 10 days following a unilateral frontoparietal fluid percussion (F-P) injury (3.7-4.3 atm). Compared to sham controls, animals exhibited bilateral hypermetabolism immediately following brain injury. However, this effect was more pronounced in structures ipsilateral to the site of F-P and was especially marked for the cerebral cortex (46.6-30.1% higher than control) and hippocampus (90.1-84.4% higher than control). By 30 min post-trauma many ipsilateral regions still showed evidence of hypermetabolism, although their lCMRglc had subsided. Beginning as early as 6 h following injury many regions within the ipsilateral cortex and hippocampus went into a state of metabolic depression (16.4-33.7% of control) which lasted for as long as 5 days. These results indicate that, although not mechanically damaged from the insult, cells exposed to concussive injury dramatically alter their metabolic functioning. This period of post-concussive metabolic dysfunction may delineate a period of time, following injury, during which cells are functionally compromised.