Although stereotypy is one of the key diagnostic features of autism, few studies have compared stereotypic behavior in children with autism and typically developing children. The present study employed direct observational measurement methods to assess levels of stereotypic behavior in 2-, 3- and 4-year-old children with autism or pervasive developmental disorder - not otherwise specified (PDD-NOS) and age-matched typically developing peers. Thirty children with autism or PDD-NOS and 30 typically developing children participated. Each child's performance of several early learning and play skills was assessed using a direct observational assessment protocol developed for children with autism who were entering early intensive behavioral treatment. Duration of episodes of vocal and motor stereotypy was recorded from a videotaped 10 min portion of that assessment session. Results indicated that the 2-year-old children with autism or PDD-NOS had somewhat higher levels of stereotypic behavior than the typically developing 2-year-olds, while the 3- and 4-year-old children with autism or PDD-NOS displayed substantially higher levels stereotypic behavior than their same-age peers.