This study examined repetitive and stereotyped behaviors (RSB) in children with autism spectrum disorders (ASD, n = 50), developmental delays without ASD (DD; n = 25) and typical development (TD, n = 50) between 18 and 24 months of age. Children with ASD demonstrated significantly higher frequency and longer duration of RSB with objects, body, and sensory behaviors during a systematic behavior sample than both the DD and TD groups. RSB with objects were related to concurrent measures of symbolic capacity and social competence in the second year and predicted developmental outcomes as well as severity of autism symptoms at 3 years in children with communication delays. RSB in the second year appear to be important for early identification and prediction of developmental outcomes.