It is important to the neurologist to have in mind the possibilities o a patient to have a congenital arterio-venous anomaly, since its diagnosi and its treatment is possible today. The nomenclature has been reaso for confusion; the authors prefer the term congenital arterio-venous anomaly but the most common in the literature is congenital arterio-venous aneurysn. The work of Virchow is the anatomical basis for the study of thi malformation, which is due to congenital disgenesis lesion with progrei sion in its evolution. The physiopathology shows that the lesion is dynamic, of local effects, mainly poor bloody circulation, and general effect upon the circulatory system; the signs and symptoms are therefore due to modifications of the circulation and the intrinsic development of the lesion. The symptomatology presents neurological and circulatory aspects. Th neurological signs are the most important; convulsions followed by localize neurological signs as progressive hemiparesis, subarachnoid hemorrhage an migraine associated with neuro-psychiatric disturbances, should be suspecte as data for early diagnosis. The arterio-venous anomaly is a progressiv disease tending to provoke subarachnoid hemorrhage. Angiography is th best diagnostic procedure. The best treatment at present time is the complete removal of th anomaly. The therapeutic results will depend on the early diagnosis, an therefore the main responsability will belong to the clinician who make the diagnosis than to the neurosurgeon who operates on. Earlier the diagnosis, better the results, and fewer the neurological sequelae.