This study estimates the sensitivity and specificity of the social communication questionnaire (SCQ) for autistic spectrum disorders in preschool children at high risk for developmental problems referred to a tertiary centre and compares the predictions of the SCQ and the referrer. The SCQ was completed by 81 parents prior to multidisciplinary assessment and compared with the final diagnosis. The sensitivity and specificity were 93% and 58% for children aged 2-6, and 100 and 62% for children aged 3-5 years, with a cut-off score of 11. The SCQ performed better than referrers. Low-specificity means the SCQ is not suitable as a diagnostic tool but will assist clinicians and tertiary services in selecting children with developmental problems who require autism-specific assessment.