Autism is one of the pervasive developmental disorders. It is a neuropsychiatric disorder of brain function, which can be defined on behavioral criteria reflecting abnormal development of social interaction, communication and imagination.This study was carried out in the National Research Center, Department of children with special needs (CSN). It aimed at estimation of the polyunsaturated fatty acids in autistic children before and after taking the supplement for 3 months and evaluation of the effect of this supplement on the behavior of autistic children.The present study is applied to thirty autistic children (18 males and 12 females) affected by autism ranging in age between 3-11 years and 30 healthy children in the same age range as control group.The present study revealed that polyunsaturated fatty acids in the whole blood was significantly lower in autistic children before the supplement, the polyunsaturated fatty acids level showed a significant improvement in the plasma of autistic children after taking the supplement for 3 months. Some of these children showed also a clinical improvement regarding their autistic behavior.