Fatigue is the most common and frequent symptom that people experience, yet the field of medicine has not paid all that much attention to it until the past decade or so. One can appreciate the relative lack of coverage for fatigue if one contrasts the number of texts on pain to the number of texts on fatigue. Isolating a patient’s specific aetiology of fatigue may be exceptionally difficult because of a multitude of contributing factors which may be involved. This book examines the physiologic/pathophysiologic mechanisms, assessment and treatments of fatigue.