Objectives The European Autism Information Systems Project (Posada & Ramirez, 2008) highlighted the lack of systematic and reliable data on the prevalence of autism spectrum disorders in Europe. The EAIS project designed a protocol for the study of ASD prevalence at European level to facilitate a common format for screening and diagnosing children across the EU. This is the first study to operationalise the screening phase of the protocol and validate the use of a screening instrument the Social Communication Questionnaire (SCQ: Rutter et al., 2003) as a primary screener for ASDs among national school children. Methods A study booklet completed by the parents of eligible children aged 6-11 years was returned to the teacher for collection by the study team. There were (n = 7,951) primary school children screened males 54% (n =4,268) females 46% (n = 3,683), special education school children (n = 189) males 66% (n = 125) females 34% (n = 64), in three regions: Galway, Waterford and Cork. Participation rates for parents of eligible children were 69% (n=5,457) for national schools, 36% (n=69) for special education schools. Results The distribution of SCQ total scores for the national school sample were strongly skewed towards lower scores 4.65 ± 4.75, range 0-36. The majority of children (92%) scored in the normal range (0 to11) (n = 5002), moderate (12-14) (n = 225) 4%, high (>15) score range 4% (n = 230). An optimal cut off score (>13) differentiated ASD from other diagnosis sensitivity 0.90, specificity 0.81, positive predictive value 0.43, and negative predictive value 0.98. Test re test reliability mean interval: 15 months, Pearson’s r of 0.77, df = 499, p < 0.001. Conclusions The feasibility of screening children for ASDs with the EAIS protocol, using the SCQ in a non-clinical setting of Irish primary and special schools was demonstrated.