This project will directly compare two different interventions in families with a child at risk for developing autism at 18 months of age. The first is a parent-implemented intervention (PII) offered in 3 weekly sessions for 6 months. It will teach parents how to embed strategies to support social communication skills for 25 hours a week within everyday activities. The second is an information, education, and support group (IES) offered twice monthly for 6 months. Specifically, this study will compare the effectiveness of PII and IES; and also to compare the effectiveness of entry in PII at 18 and 24 months of age. This study will document growth trajectories for very young children with autism spectrum disorders (ASD) receiving a manualized intervention that can be implemented by families. Child development in areas of social communication, adaptive and overall functioning, and specific symptoms of autism will be monitored until the child turns 3 years old. In addition, it will provide information and possibly evidence that supporting intervention beginning at 18 months leads to better outcomes than beginning at 24 months, supporting the need for early autism screening.