Background: Autism Spectrum Disorder (ASD), sometimes referred to as “autism", is “a chronic disorder whose symptoms include failure to develop normal social relations with other people, impaired development of communicative ability, lack of imaginative ability, and repetitive, stereotyped movements". Objective: To assess the clinical and laboratory characteristics as well as risk factors of ASD. Patients and methods: The study was a retrospective descriptive cohort study and included 1650 autistic patients with AD/ASD referred to the Pediatric Department and Psychiatry Outpatient Clinic at Sohag University Hospital, Egypt, and followed up during the period from June 2019 to May 2020. Results: Age at presentation ranged from one month to 252 months with a mean ± SD of 44.496 ± 28.435. The results of IQ of the studied patients were available in 241 patients with a range from 25 to 100 with a mean IQ of 62.98. Our CARS data were available in 920 of the studied patients (n=920) and showed a mean of 30.064 with a range from 20 to 60. In our study, the associated risk factors of autism were reported in 332 patients. Hearing problems were found in 25.9%, neonatal asphyxia in 15.9%, phenylketonuria was found in 11.8% of those patients. Epilepsy was found in 7.8%, hyperammonemia in5.3%, cerebral malformation in 5.1%, down syndrome in 3.3%, and tuberous sclerosis in2.8%. Conclusion: Our study confirmed diagnosis of ASD in children affects patients, family, and the community at large. Knowledge of ASD is crucial for health professionals as its prevalence is increasing globally.