Background: Autism is a developmental disability characterized by severe deficits in social interaction and communication. Although the exact cause of autism spectrum disorder (ASD) is still not known, it is believed that both genetic and environmental factors influence the onset and development of this disorder. Aim of the study: To assess the possible environmental risk factors and the levels of aluminum, mercury and lead in the hair of children with ASD. Patients and methods: A case control study was carried out. Thirty ASD children were studied in comparison to 30 age- and sex-matched controls. All participants were subjected to a questionnaire for data collection, clinical evaluation and hair sample for measurement of level of aluminum, mercury and lead which reflects past exposure. Results: The mean age of the studied autistic children was 6.5±2.4year compared to 5.4±1.8 year in the controls with no significant difference (P>0.05), 76.7% of the cases were boys. Living near to traffic was found to be higher among cases than among controls with p <0.05 indicating high statistically significant difference. A short distance (> 500m) between the house and nearby traffic was another risk factor. Autistic children were found to play with wall paint more than the controls with high statistical difference between them. The use of aluminum cooking utensils and spoons was significantly higher among families of cases than controls. The mean level of aluminum was significantly higher in cases compared to the control (20.79±10.2, 7.85±1 respectively with P<0.0001). Mean level of mercury among cases was significantly higher than among controls (1.24±1.12, 0.22±0.147 respectively). Cases also had significantly higher levels of lead compared to controls but they were within the normal levels. Conclusion: Aluminum and Mercury were significantly higher in cases compared to controls.