Background: Increasing rates of autism spectrum disorder (ASD) have contributed to lengthy waits for expert diagnostic assessment that negatively impact ASD outcomes. Many ASD diagnostic guidelines state that an expert team is needed to make the diagnosis; although some children currently receive their diagnosis from a community-based clinician, e.g. a general paediatrician (GP). There are no studies of the accuracy of GPs in diagnosing ASD. Project aims: The aims of this project are to: 1) determine accuracy of GP ASD diagnosis compared to an expert team assessment; 2) to determine case features associated with accurate diagnosis by GPs. Possible features include: child's age; sex; cultural background; ASD severity; developmental delays; and use of tools in the assessment. Methods: We will recruit twenty GPs from across Ontario, as well as 200 of their patients (10 per GP) who have been referred with possible ASD. The GP will complete his/her assessment and decide on a diagnosis, but will not tell the family. The ASD expert team, consisting of a developmental paediatrician, a psychologist, and a speech-language pathologist, will then perform a diagnostic assessment without knowing the GP's opinion. The team will inform the family of their diagnostic opinion. We will determine the diagnostic agreement between the two assessments. We will then determine which of the child's characteristics (age, sex, cultural background, ASD severity, developmental delays) predict agreement in diagnosis. Expected Results: Results from this study will determine whether GPs can independently and accurately diagnose ASD. Future activities include refinement of educational workshops for GPs on ASD diagnosis and development of pathways to identify which children can be diagnosed in a community setting.