Design: In this explorative study fatigued disease-free cancer patients (n=57), who finished treatment for cancer at least one year and maximally ten years ago, will be approached for this study and asked for informed consent. They will be compared to age and sex matched non-fatigued patients (n=21). First, a base-line assessment will take place, which includes magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) to assess brain morphology and brain metabolites, respectively. To assess peripheral and central fatigue a two-minute endurance test will be administered at maximal voluntary (isometric) contraction (MVC). During the test changes in EMG and force indicate peripheral fatigue, while central fatigue is studied by the twitch interpolation technique. A maximal exercise test will be performed to assess physical fitness and deconditioning. At baseline patients will also be given an actometer which will register daily activity during two weeks. Further, the actometer will register daily activity up to five days after the maximal exercise test. Finally, at baseline patients will fill out a standardized questionnaire, including the Checklist Individual Strength and a self-observation list to assess fatigue severity. Then, the fatigued patients start immediately with Cognitive Behaviour Therapy (CBT). At the end of the therapy, after 6 months, a second assessment will take place in this group of patients. The assessment consists of the same measurements as at baseline. The results will be compared with the baseline situation to analyze the effect of CBT on the (neuro)physiological parameters.