Alexithymia is a term meaning "no words for mood." It has been applied to patients who have marked difficulty in verbal expression of emotions and limited ability to use fantasy. These patients often have psychosomatic illnesses and tend to do poorly in traditional dynamic psychotherapy. The concept is discussed from an historical perspective and its current status in the understanding of psychosomatic illness is assessed. The alexithymia literature is critically reviewed with a focus on definition, measurement, etiological speculations, and the relevance of alexithymia to the psychotherapeutic process. The alexithymic concept has much to offer heuristically, but most of the literature to date has been anecdotal and theoretical, with few research investigations. Suggestions are made for future research that could serve to validate the concept and provide answers to questions regarding symptom formation and psychological problems.