This study involves sample collection to identify biomarkers relating to Autism Spectrum Disorder(ASD) in the saliva of children who are between the ages of 18 months to 6 years and 11 months. Participants will at each timepoint have a non-invasive saliva swab collected and complete a brief demographic and medical history questionnaire as well. Children in the pediatric/provider setting who will receive a referral for an ASD diagnosis because they were determined to have a suspicion of developing ASD will be enrolled in the study. Children will also be enrolled in the specialist evaluation setting where they will receive a DSM-5 diagnosis. A subset of both enrollment cohorts will also be followed up with at a third time point in which their diagnosis will be confirmed, and information about any ongoing treatment will be gathered.