This funding opportunity announcement (FOA) solicits the Small Research (R03) grant mechanism for the support of research designed to elucidate the diagnosis, epidemiology, etiology, genetics, treatment, and optimal means of service delivery in relation to Autistic Disorder ("autism") and autism spectrum disorders (Rett's Disorder, Childhood Disintegrative Disorder, Asperger's Disorder, Pervasive Developmental Disorder-Not Otherwise Specified, or "Atypical Autism").