Cancer of the breast is the commonest from of cancer of women in Denmark and the incidence is increasing. At present, a series of risk and prognostic factors are recognised. These are primarily related to the endocrine system. Other factors, including the significance of psychological and social factors, have been investigated. A review of the literature concerning the significance of psychological and social factors as risk and prognostic factors, respectively, reveals that the methodological problems in these investigations are considerable and multifarious. On the basis of a review of the literature, it is concluded, that there is no proof that psychosocial factors influence the disease of cancer of the breast. Nevertheless, certain evidence exits in the literature suggesting a connection between inhibition of aggression and an introverted personality and the development of cancer of the breast while, in some investigations, ability to cope has a certain significance as a prognostic factor. Investigations of psychosocial intervention as the actual antineoplastic treatment are very few and the results are difficult to interpret. It may be concluded that no basis exists to justify employment of psychosocial intervention as an actual form of treatment with the object of improving survival.