The goals of this diagnostic study are to determine how accurate general pediatricians are in autism spectrum disorder (ASD) diagnostic assessment and which children might be best suited for this type of assessment. The investigators will also evaluate the use of a new virtual diagnostic tool, the Autism Assessment for Preschoolers with Language Element Sequence (AAPLES). The investigators will recruit twenty general pediatricians from across Ontario, Canada, as well as 200 of their patients (maximum 10 per pediatrician) who have been referred with possible ASD. The general pediatrician will complete their assessment and decide on a diagnosis, but will not tell the family. The ASD expert team, consisting of a developmental paediatrician and a psychologist, will also perform a diagnostic assessment without knowing the general pediatrician's opinion. The team will inform the family of their diagnostic opinion. Investigators will determine the diagnostic agreement between the two assessments. They will then determine which of the child's characteristics (age, sex, racial/ethnic background, ASD features, developmental delays, having a sibling with ASD) predict agreement in diagnosis. Some children in the study will have the option of undergoing an additional virtual autism diagnostic assessment using the AAPLES. The clinician administering the AAPLES will not know the results of the other assessments. The investigators will measure diagnostic agreement between the clinician administering the AAPLES and the expert team.