Purpose: Epidemiological studies have shown that a wide range of outcome trajectories exist in ASD, but little is known about their determinant in a long-term perspective. The EpiTED cohort was set-up in order to understand the heterogeneity of developmental trajectories among children with a diagnosis of PDD and the role of clinical, biological and environmental factors in their adaptive outcome. It is one of the rare cohorts involving a long term prospective follow-up based on a large set of variables, and precise phenotypes of the entire autism spectrum.