The use of amobarbital sodium (amytal sodium R) as a diagnostic test for brain disease is described. In 57 of 88 patients with proven brain disease, who on clinical examination showed no disturbances in behavior, the intravenous administration of the drug produced patterns of disorientation for time, place, and person and denial of illness. These changes were not obtained in any of 50 control patients. The applicability of the procedure to the study of alterations in brain function caused by structural, iatrogenic, metabolic, and toxic agents is discussed.Abstract Teaser