The article describes a pilot and follow-up study of the preliminary development of a new tool to screen for Asperger syndrome (AS) and related social and communication conditions (the Childhood Asperger Syndrome Test, CAST) in children aged 4-11 years, in a non-clinical setting. In the pilot study, parents of 13 children with AS and of 37 typically developing children completed the CAST. There were significant differences between the AS and typical sample means. The pilot was used to establish preliminary cut-off scores for the CAST. In the main study, parents of 1150 primary-school-age children were sent the CAST, and 174 took part in the full data analysis. Results suggest that compared with other tools currently available, the CAST may be useful for identifying children at risk for AS and related conditions, in a mainstream non-clinical sample. Further research is ongoing.