The aim of this study is to investigate whether greater occipital nerve stimulation is effective in the treatment of fibromyalgia related pain. The study uses sub sensory threshold stimulation and placebo stimulation in order to investigate whether sub-threshold stimulation is feasible in a placebo controlled study.

Inclusion Criteria:

• Diagnosed according to the criteria of the American College of Rheumatology (ACR-90)
• Minimally treated with adequate trials during 3 months
• Insight of the patient in her disease and capable of understanding and signing an informed consent

Exclusion Criteria:

• History of severe illness or suffering from severe chronic disease
• History of substance abuse, unless treated and in remission during 6 months
• Cardiac disease
• History of epileptic insults
• Psychiatric disorders with psychotic symptoms
• Pace maker / defibrillator
• Pregnancy