A decade and a half have elapsed since DSM-IV and ICD-10 appeared. During this time the convergent definitions of autism and related disorders in these two diagnostic systems have stimulated tremendous research. In this brief review we summarize areas of progress and continuing controversy, including approaches to diagnosis in more cognitively able individuals on the autism spectrum, diagnosis in very young infants, the issue of subtypes, and the potential contribution of genetic research. The use of dimensional assessments has some advantages as do the insights from prospective studies. At this point it will be important to study not only causative factors but developmental processes disrupted in these disorders.