As has been shown by a number of working groups, primary fibromyalgia syndrome does not represent a single clinical entity. It is possible to distinguish between a subgroup with high pain sensitivity and no associated psychiatric condition, a second subgroup characterized by depression and concomitant pain symptoms associated with fibromyalgia syndrome, and a third group with somatoform pain disorder of the fibromyalgia type. Bland inflammatory processes must be considered as the cause in the first group, while depression is the underlying reason for the development of pain in the second group. In the third group, serious previous or still existing psychological problems or also insufficient coping with illness symptoms must be regarded as the reason for pain chronification. Group 1 benefits from a blocking of the 5-HT3 receptors by means of tropisetron, for example. This not only affects pain chronification but also the inflammatory process itself. Group 2 needs antidepressant treatment, whereas the focus should be on psychotherapy is group 3. Groups 1 and 2 will also profit from multimodal physical treatment programs; to a certain extent this applies to group 3 as well. So-called mixed types require a combination of therapeutic measures.