Autism spectrum disorders (ASDs), particularly the high incidence conditions of autism, PDD NOS, and Asperger's Syndrome, have become increasingly popular topics of study in the mental health field. Traditionally, the focus has been on young children and early recognition and diagnosis. However, given that these conditions are life long in nature, continued assessment in not only advisable but essential. This review covers diagnostic issues as they pertain to adults with high incidence ASD. The current state of nosology and diagnosis in adults with ASD is reviewed. A discussion of pragmatic diagnostic issues and future research needs are covered.