Pain patients are defined as patients with a somatoform disorder due to DSM-IV, if chronic pain lasts for at least 6 months in several anatomical regions. Somatoform disorders (DSM-IV) have the presence of physical symptoms that suggest a general medical condition but that are not fully explained by a general medical condition, by the direct effects of a substance, or by another mental disorder. The symptoms must cause clinically significant distress or impairment in social, occupational, or other areas of functioning. The physical symptoms are not under voluntary control. Psychic factors exclusively or in combination with a medical disease factor influence onset, severity, exacerbation or maintenance of symptoms decisively. A subgroup of somatoform disorders, i.e., fibromyalgia, is a common nonarticular rheumatic syndrome characterized by myalgia and multiple points of focal muscle tenderness to palpation (trigger points). Muscle pain is typically aggravated by inactivity or exposure to cold. This condition is often associated with general symptoms, such as sleep disturbances, fatigue, stiffness, headaches, and occasionally depression. There is significant overlap between fibromyalgia and the chronic fatigue syndrome. Fibromyalgia may arise as a primary or secondary disease process. Interleukins IL-1ß, IL-6 und tumor necrosis factor-a have been detected in the skin of these patients. Blockade of the 5HT3 receptor has been reported to alleviate chronic pain in tendopathy, fibromyalgia and autoimmune diseases. However, only a subgroup of patients responds to this therapy. It is supposed that patients with somatoform disorders (DSM-IV) diagnosed according to clinical criteria consist of immunologically heterogenous groups. However, up to now, the immunologic and genetic background of patients with somatoform disorders classified via DSM-IV has not been systematically evaluated. The study concentrates on the psychometric characterization of patients with pain disorder focusing on depression, anxiety, coping behavior, psychic trauma, alexithymia and somatoform symptoms. The present study is performed to define subgroups of patients with somatoform disorders (DSM-IV) by immunological, pyschologic and genetic characterization which may benefit from potential 5HT3 receptor antagonists or anti-inflammatory therapy.