Alexithymia refers to a specific disturbance in psychic functioning characterized by difficulties in the capacity to verbalize affect and to elaborate fantasies. Although initially described in the context of psychosomatic illness, alexithymic characteristics may be observed in patients with a wide range of medical and psychiatric disorders. The author reviews the concept of alexithymia, including its historical background, clinical and demographic features, and possible etiology. He critically evaluates the different methods used to measure alexithymia and discusses the important implications it has for medical and psychiatric treatment.