Anxiety is both an innate and a constructed response to perceived and anticipated threat. This chapter explores anxiety as signal, symptom and syndrome, and describes the evolution of the major psychodynamic models of signal anxiety. The major psychodynamic models of signal anxiety posit anxiety as a signal of unconscious, intrapsychic danger. Neurobiological factors also contribute to the development and expression of anxiety symptoms and syndromes. Imaging techniques have been used to illustrate the presence of unconscious processes that to date have only been hypothesized; specifically that unconscious affects are a crucial determinant of behavior. Many symptomatic patients were forced to make adaptations to internal and external threats in early childhood. Ironically, the treatment of symptomatic anxiety may create an anxiety of its own, the anxiety about change. Many patients present with the acute onset of anxiety symptoms but do not meet the criteria for an Axis I anxiety disorder.