The heritable nature of autism has been borne out by research showing that identical twins and siblings of children with autism are at a greater risk of the disorder than children in the general population. Dr. Warren and his colleagues plan to follow 66 such school-aged siblings to gauge cognitive, language, and behavioral outcomes. Siblings of children with autism often show signs of language and social vulnerabilities at around 16 months old, younger than the age at which autism is typically diagnosed. This may represent early features of autism or broader related disorders. It is clearly important to monitor vulnerable siblings from an early age, but follow-up studies are needed to determine whether these early difficulties tend to persist or can be overcome through maturity or intervention. The researchers plan to address this by taking advantage of a prior study of early social and emotional development in 1- to 2-year-old siblings of children with autism and age-matched healthy controls. The new study will follow the same children, who are now 5 to 6 years old, over the course of two years, tracking their development in terms of organization, self-control, ability to relate to others, and other cognitive and behavioral functions that are often deficient in children with autism. Warren and colleagues plan to look for relationships between the children's early social and emotional profiles and any social or behavioral difficulties they experience later in life.