The concept of anxiety is defined and is followed by the presentation of a number of problems amongst which are questions such as—to what extent is anxiety the result of heightened instinctual tension due to frustration and whether or not anxiety is primarily a tension phenomenon or a mode of discharge. The author then proceeds to review the development of Freud's views on the subject of anxiety. This is a comprehensive account of Freud's transition from his earlier physiological theory of anxiety to the later psychological one. In