Asperger syndrome (AS) is a disorder on the continuum of autistic spectrum disorders characterized by a lack of social reciprocity and empathy, and severe difficulties in social integration. Controversy remains as to what constitutes AS and whether it should be declared a separate disease or higher-functioning autism. This review discusses the contributions made by Hans Asperger and Leo Kanner in first delineating the condition, and examines the syndrome's incidence, prevalence, and etiologies. Recent studies using neuroimaging are described, along with current diagnostic and treatment options.