The present longitudinal study examined the utility of the screening tool for autism in 2-year-olds (STAT) in detecting autism spectrum disorder (ASD) in toddlers who are less than 24 months of age. The study sample, which consisted of 119 toddlers with developmental problems, were assessed when they were between 16 and 24 months of age (Time 1) and after a period of 18 months to finalize the diagnosis (Time 2); 57 children had ASD and 62 children had developmental delays. A cutoff score of 2.5 on the STAT yielded an optimal combination of high sensitivity and specificity. The STAT demonstrated adequate predictive validity in detecting ASD in Taiwanese toddlers who are less than 24 months of age.