Persons with Autism Spectrum Disorder (ASD) demonstrate persistent deficits in social communication and social interactions, and restricted, repetitive patterns of behavior, interests, or activities.This work aimed to analyze clinical and environmental severity factors of ASD. It is a transversal study which was initiated in January 2012 and has lasted 36 months. Fifty children diagnosed with ASD were recruited at child psychiatry consultation at the University Hospital in Fes, Morocco. All children were assessed using a standardized procedure : Anamnestic, clinical, paraclinical and therapeutic data were collected and they were evaluated for ASD severity using the Childhood Autism Rating Scale (CARS).After overall description of clinical sample characteristics of children, we analyzed the relationship between some clinical and environmental factors and child symptom severity.Clinical factors which were analyzed in this study are : Femal sex, absence of langage,presence of intellectual deficiency, inability to imitate, presence of repetitive and restricted behavior (RRB), comorbidity with epilepsy, genetic pathology, attention deficit/hyperactivity disorder ( AD/HD) and with sleep problems. Absence of langage (p<0,001), inability to imitate (p<0,001),and RRB (p=0,017) were significantly associated with higher ASD severity.We also examined associations between advanced parental ages at child birth, parental incomes, mother time slot, fetal distress, age at ASD diagnosis on ASD severity. The only environmental factor which was significantly associated with ASD severity was father income (p=0,017). This analytical study allowed to determine some clinical and environmental factors associated with ASD severiry. The goal is to offer adequate treatments and therapies for children with ASD depending upon these factors and severity degree