This paper is an elucidation of the phenomenon of repetitiveness as the nuclear problem of neurosis. Some of the points argued are: (1) repetitiveness is the essence of all instinctual activity; (2) all psychological phenomena are by nature repetitive; (3) all neurotic phenomena are a distortion of normal repetitiveness; (4) obsessional neurosis is a special form of neurotic distortion of the mechanism of repetitiveness wherein the drive is experienced consciously. The last point differs from Freud's concept of obsessional neurosis as specific in itself. The phenomena of repetitiveness are discussed from physiological, pathological and psychopathological viewpoints. A tentative outline of reclassification of the neuroses based on the theory of repetitiveness is offered.