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 and a third subgroup characterized by depression associated with fibromyalgia syndrome, and a fourth group with somatoform pain disorder of the fibromyalgia type. Mild inflammatory processes must be considered as the cause in the first group, while depression is combined with fibromyalgia in the second and the third group. In the fourth 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 does not only affect pain chronification but also the inflammatory process itself. Group 2 and 3 needs antidepressant treatment, whereas the focus should be on psychotherapy in group 4. Groups 1, 2 and 3 will also profit from multimodal physical treatment programs, to a certain extent this applies to group 4 as well. So-called mixed types require a combination of therapeutic measures.