Rasmussen's encephalitis is a neurological disorder probably of immunological origin, characterized by intractable epilepsy, neurological deterioration and the presence of antibodies against R3 glutamate receptors.To present the experience of an Argentinian Paediatric Neurology Service during the past 7 years.We analyzed the clinical histories of 12 patients with RS as defined by the diagnostic criteria proposed by Hart et al. We evaluated the following parameters: neurological examination, neuropsychological assessment, types of crises, age of onset, frequency, distribution, electroencephalogram, video EEG, evoked potentials, neuro-radiological studies; CT and cerebral MR using gadolinium, SPECT, lumbar puncture and cerebral biopsy.The crises were of simple partial motor type in 12 cases, secondarily generalized partial crises in 7 cases, complex partial crises in 4 cases and partial and generalized motor states in 8 cases. RESULTS. The ictal EEGs during the continuous partial crises showed contralateral focal slow activity of the affected side of the body in 30% of cases. The neuro-radiological studies (CT and MR) showed signs of cerebral hemiatrophy in all 12 cases, hyper-intense images in the T2 sequences of the fronto-temporo-parietal regions in 5 cases, an asymmetric megacisterna magna in 1 case and hypoplasia of the cerebellar vermis in another case.The continuous partial crises showed little correlation with the electro-encephalography. Following administration of i.v. gammaglobulin there was a transient halt in progression of the neurological deterioration and control of the crises in 55% of the cases. Surgery continued to be the treatment recommended for control of the epileptic crises.