This is a review of autism spectrum disorders. It presents the symptoms of the disease discussing the age of diagnosis and first symptoms encountered. It is a polygenic disease that occurs mainly in boys. The importance of early diagnosis is emphasized. The assessment scales used for early diagnosis are discussed. The anatomic basis of the disease is detailed. The molecular genetic aspects, and the techniques employed are reviewed. Special emphasis is placed in chromosome abnormalities observed in autism. Its incidence worldwide is increasing dramatically. This is considered to be due to epigenetic events. Several hypotheses for such epigenetic processes are discussed. Finally the state of intervention in autism and its paradigms are detailed. (J Pediatr Neurol 2003; 1(2): 55–67).