Anxiety is the central affect of every therapeutic relationship. Both the patient and the therapist must engage with it if their work is to have meaning. Anxiety can destructively threaten the therapeutic relationship, but it can also give it constructive significance. Through a presentation of the development of theory from Freud to the Kleinian tradition, as well as to representational and mentalization theories and to infant and attachment research, the author approaches the phenomenon of anxiety. She then complements the theory with experiences from therapeutic practice by addressing psychopathology and typology of anxiety disorders, the function of anxiety in transference and countertransference, and the relationship between anxiety and courage. A symptom-oriented typology is supplemented by a psychodynamic perspective on central anxiety situations in the therapeutic process.