The authors present a review of the role of psychological factors in peptic ulcer disease (PU). Three lines of research have been identified: personality, psychological factors and PU; stressful life events and their relationship to PU; possible interactions between biological parameters, the CNS and psychosocial aspects. The analysis of the studies presented shows that there is a certain level of agreement with regard to personality and psychological aspects; PU patients present a personality with dependence/independence problems and high level of anxiety. Data concerning the role of stress appear to be far from uniform and often even contradictory. Much remains to be done with respect to the possible links between psychological and biological parameters; there have been only few studies in man--which have not been duplicated and were performed on a limited number of patients--but a fair number in animals. However, the results concerning the relationship between psyche and secretory patterns are very interesting, and represent one of the most important lines of future research.