Anxiety symptoms and disorders are associated with a range of general medical disorders. This association may be a physiologic consequence of the general medical disorder, a psychologic reaction to the experience of having a medical illness, a side effect of treatment, or a chance occurrence. This article briefly reviews the associations of panic disorder with seizure disorder, Klüver-Bucy syndrome, mitral valve prolapse, and respiratory disorders; of generalized anxiety disorder with chronic obstructive airway disease and cardiovascular and endocrine disorders; of social anxiety disorder with Parkinson's disease; of obsessive-compulsive disorder with striatal disorders; and of posttraumatic stress disorder with head injury and pain. Such associations provide important clues for understanding the neurobiology of anxiety disorders.