Background: Epilepsy is a chronic disorder of the brain that affects people of all ages Neuropsychological impairment is an important comorbidity of chronic epilepsy in the majority of children with epilepsy. interictal epileptiform EEG discharges may present as a complicating factor in spite of being seizure free. In a group of children with interictal EEG discharges there is sudden and unexpected decline of school performance as the first symptom of epilepsy. Consequently, accumulating cognitive impairment, and even a decline in IQ scores, is reported in epileptic children with frequent episodes with epileptiform EEG discharges. Aim of the Work: To evaluate the possible relationship between interictal EEG discharge and cognitive    function in a sample of Egyptian epileptic children. Patients and Methods: The ethical approval was obtained from the Hospital Ethical Research Committee. Each patient and/or parents entering the study signed an informed consent. This study was conducted on 140 children selected from Epilepsy Outpatient Clinic of Al-Azhar University Hospitals during a period of two years starting from June 2016 untill June 2018. A specialized pediatric neurology sheet was taken. EEG and cognitive assessment of epileptic patients with and without epileptiform EEG discharges using Stanford-Binet intelligence scale and P300 by ERP were performed to each patient two times 3 months in between. Results: we found that patients with frequent IEDs had high mean P300 latency and low IQ when compared to patients with infrequent and normal EEG examination. In addition, the mean p300 latency significantly reduced with rising in IQ (more improvement in cognitive function) after disappearance of IED in some patients. Conclusion: Interictal epileptiform EEG discharge had an additional effect on cognitive function especially if generalized and of high frequency. This effect might be often underestimated and might accumulate, and have a severe cognitive impact. So, treatment of epileptic patients should put in concern reduction or even treatment of IEDs as controlling of these IED lead to improvement of cognition.