Questions have been raised about the significance of restricted and repetitive behaviors (RRBs) in predicting outcomes of children with Autism Spectrum Disorders (ASDs). Previous studies have yielded mixed findings, but some suggest that the presence of RRBs during preschool years is a negative prognostic indicator for later childhood. This study examined the effect of RRBs at ages 1-2 and 3-5 years on cognitive functioning, adaptive abilities, and ASD symptomatology at age 8-10 years in 40 children with ASDs. At 1-2 years, RRBs did not predict later functioning. However, at 3-5 years, more severe preoccupations with parts of objects, sensory interests, and stereotyped motor movements predicted less developed cognitive and adaptive skills, and greater ASD symptom severity at age 8-10 years.