Fatigue is a disabling symptom common to many neurologic conditions, including Parkinson disease, post-stroke syndromes, and traumatic brain injury. Fatigue in the neurologic population is defined differently from that in the general population, and this has implications for assessment, research, and treatment. A considerable amount of research has been done in recent years aiming to describe, quantify, and ultimately treat this problem. There are relatively few proven treatments for fatigue in these populations, but the mainstays of therapy can be divided into pharmacologic and nonpharmacologic approaches.