This retrospective clinical study aimed to study the differential effect of epilepsy in the patients diagnosed having a pervasive developmental disorder (PDD) with respect to certain clinical features of autism. The patient group included the cases with a determined etiology or some neurological involvement as shown by the neurological examination and neuroimaging findings as well as idiopathic cases. The study included 83 patients,67 boys and 16 girls. There were 49 patients (59%) with epilepsy and 34 patients (41%) without epilepsy. The variables considered were, biodata, consanguinity, detailed behavioral features such as abnormal reactivity to sensory stimuli, presence of unusual fears, emotional lability, language features and EEG findings. As regards significant results, fine motor coordination problems, non-verbal communication problems,self-care problems, delay in walking and hyperactivity were significantly high in the epileptic group (group E) while echolalia,phobia , neologism, neonatal problems, nocturnal enuresis and family history were significantly high in the non-epileptic group (group non-E).