This book reviews the literature on fatigue in general and in cancer. A chapter is devoted to identifying the concept of fatigue in cancer patients in comparison to fatigue as experienced in healthy individuals. Descriptors derived from this conceptional analysis were compared to those known from existing measurement tools, as published in available literature. A new fatigue assessment questionnaire was then developed and tested. In another study, this instrument underwent further reliability and validity testing. At the same time, a theoretical framework of fatigue emerged. The last chapter synthesizes the findings of the consecutive studies, and the appendix contains the Fatigue Assessment Questionnaire. This book is a must for reseachers, oncology nurses, physicians and psychologists who deal with this relevant aspect of quality of life in cancer patients.