Background In the years around 1990,in Beijing Tiantan Hospital Affiliated to Capital Medical University many children with infantile hemiplegia and intractable epilepsy were treated with further modified anatomical hemispherectomy.We report the follow up of the first six cases.To make good use of these precious clinical data and make clear their neuropsychological state,we performed neuropsychological and neurophysiological measurements in these patients,who were at a median of 17.8 years after hemispherectomy.Methods Oddball task was given to the patients and to a normal control group to collect the peak latency(PL)and peak amplitude(PA)of event-related potentials(ERPs)-P300.The P300 data of the two groups were analyzed and the P300 patterns of the six patients are presented.The baseline characteristics and long-term follow-up of the six hemispherectomized patients,especially the long-term seizure control and cognitive function after surgery,are described.Results Five patients had no seizures and one was almost seizure-free during the years after surgery.Clear P300 was obtained from every electrode in the patients.Differences of P300 between patients and normal control group had no statistical significance.And the maximum PA was at the site of electrode Pz or Cz which was consistent with that of the control group and with previous findings.Conclusions Further modified anatomical hemispherectomy has preferable long-term antiepileptic effects.The P300results of the patients mean that the basic cognitive function of the patients has no difference from the control group.This reflects the plasticity of the hemisphere to some extent and increases the affirmation of the long-term curative effects of further modified anatomical hemispherectomy from both neuropsychological and neurophysiological aspects.