This project examines the production and coordination of gestures, eye contact, facial expressions, communicative non-word vocalizations, and words in infants who, because they have an older sibling with autism, are at heightened risk for developing autism spectrum disorders (ASD). Infants will be observed monthly at home from 8 to 14 months, with follow-up visits at 18 and 24 months. The goals are to: a) document infants' changing ability to coordinate communicative behaviors; b) observe differences in communicative coordinations between situations in which the child is interacting with an unfamiliar adult and those in which interaction is with a familiar caregiver; and c) evaluate delay and/or impairment in communicative coordination in infancy as a predictor of later ASD diagnosis. Identifying indicators of autism at a significantly earlier point in development than is currently possible will allow for earlier initiation of treatment services. In addition, finding out when and how infants at risk for autism develop difficulties in integrating communicative behaviors will help us understand the nature of social communication impairments in older children with ASD and contribute to the development of more tailored interventions.