A new screening instrument for ASD was developed that can be filled out by child care workers: the Checklist for Early Signs of Developmental Disorders (CESDD). The predictive validity of the CESDD was evaluated in a population of 6,808 children between 3 and 39 months attending day-care centres in Flanders. The CESDD had a sensitivity of 0.80 and a specificity of 0.94. Based on the screening procedure used in this study, 41 children were diagnosed with ASD or got a working diagnosis of ASD. Thus, including child care workers' report on signs of ASD in screening procedures can help to identify cases of ASD at a young age.