Abstract
Recent advances in clinical research have made it possible to diagnosis autism spectrum disorders (ASD) as early as the second year of life. The diagnostic process early in development is often complex, and thus, familiarity with the most recent findings in clinical assessment instruments, early symptoms, and developmental trajectories of young children with autism is essential. This paper provides an empirically based practitioner's guide to issues and concerns related to early diagnosis of ASD in very young children, documentation of the course and patterns of ASD symptomatology in infants and toddlers, and current understanding in the field of diagnostic outcomes of children identified in the first and second year of life.