We hypothesize that epileptiform abnormalities (EA) in the electroencephalopgram (EEG) during the acute period following traumatic brain injury (TBI) independently predict first-year post-traumatic epilepsy (PTE1). We analyzed PTE1 risk factors in two cohorts matched for TBI severity and age (n=50). EA independently predict risk for PTE1 (OR 3.16[0.99 11.68]); subdural hematoma is another independent risk factor (OR 4.13 [1.18 39.33]). Differences in EA rates are apparent within 5 days following TBI. Our results suggest increased EA prevalence identifies patients at increased risk for PTE1, and that EA acutely post-TBI can identify patients most likely to benefit from anti-epileptogenesis drug trials. This article is protected by copyright. All rights reserved.