In this paper, we discussed the relationship between somatization and functional somatic syndrome (FSS). The concept of somatization takes its origin from the work of Freud S who proposed the idea of conversion as a main defense mechanism. At the same period, the term somatization was introduced by Stekel W as a hypothetical process whereby a deep-seated conflict could cause a bodily disorder. After that, Alexander F developed the emotional equivalents, which had been also proposed by Freud S, into the concept of the vegetative neurosis and psychosomatic diseases. Recently, somatization tends to be defined as 'a tendency to experience and communicate somatic distress in response to psychosocial stress and to seek medical help for it' (Lipowski ZJ, 1988). So there seems to be a strong link among conversion, somatization, FSS, and somatization disorder.