Continuous electroencephalography (cEEG) is increasingly used to detect both clinical and subclinical seizures in patients with traumatic brain injury (TBI) or subarachnoid hemorrhage (SAH). We assess whether EEG findings predict outcomes in TBI/SAH patients enrolled in a levetiracetam (LEV) vs. fosphenytoin (fos-PHT) seizure prevention trial (NCT00618436). This prospective, single-blinded, comparative trial randomized 52 patients with TBI or SAH to receive prophylactic LEV or fos-PHT. Continuous video EEG monitoring was conducted for the initial 72. h of medication administration. The association between EEG findings (degree of generalized and focal slowing, presence and frequency of epileptiform discharges and seizures) and outcomes (Glasgow Outcomes Scale-Extended (GOS-E) and Disability Rating Scale (DRS)) at discharge, 3 and 6. months was assessed using a generalized linear model. Severity of generalized slowing tended to be associated with outcomes in both treatment groups (discharge DRS, p = 0.042; discharge GOS-E, p = 0.026; 3. month DRS, p = 0.051). The presence of focal slowing, the presence and frequency of epileptiform discharges and the presence of seizures were not predictive of outcome in either treatment group (all p > 0.15). While it has been shown that LEV is associated with better outcome than fos-PHT when used as seizure prophylaxis in brain injury, aside from severity of generalized slowing, electrographic findings of focal slowing, epileptiform discharges, and seizures were not themselves associated with outcomes in patients with TBI or SAH enrolled in a randomized clinical trial. © 2011 Elsevier Inc.