Objectives: To study the ictal phenomenology, aetiology, and outcome of convulsions occurring within seconds of impact in violent collision sport. Design: Retrospective identification of convulsions associated with concussive brain injury from case records from medical officers of football clubs over a 15 year period. Subjects: Elite Australian rules and rugby league footballers. Main outcome measures: Neuroimaging studies, electroencephalography, neuropsychological test data, and statistics on performance in matches to determine presence of structural or functional brain injury. Clinical follow up and electroencephalography for evidence of epilepsy. Results: Twenty two cases of concussive convulsions were identified with four events documented on television videotape. Convulsions began within 2 seconds of impact and comprised an initial period of tonic stiffening followed by myoclonic jerks of all limbs lasting up to 150 seconds. Some asymmetry in the convulsive manifestations was common, and recovery of consciousness was rapid. No structural or permanent brain injury was present on clinical assessment, neuropsychological testing, or neuroimaging studies. All players returned to elite competition within two weeks of the incident. Epilepsy did not develop in any player over a mean (range) follow up of 3.5 (1-13) years. Conclusions: These concussive or impact convulsions are probably a non-epileptic phenomenon, somewhat akin to convulsive syncope. The mechanism may be a transient traumatic functional decerebration. In concussive convulsions the outcome is universally good, antiepileptic treatment is not indicated, and prolonged absence from sport is unwarranted. Concussive or impact convulsions are a non-epileptic phenomenon They are not associated with structural brain injury Antiepileptic treatment is not indicated In the case of sporting injury, prolonged absence from sport is unwarranted Treatment entails the appropriate management of the associated concussive injury