Sleep disorders are a relatively common occurrence after brain injury. Sleep disturbances often result in a poor daytime performance and a poor individual sense of well-being. Unfortunately, there has been minimal attention paid to this common and often disabling sequela of brain injury. This study attempts to define and to correlate the incidence and type of sleep disturbances that occur after brain injury. Consecutive admissions to a rehabilitation unit were used to create a longitudinal database designed to predict long-term outcomes for individuals who suffered a brain injury. Fifty percent of subjects had difficulty sleeping. Sixty-four percent described waking up too early, 25% described sleeping more than usual, and 45% described problems falling asleep. Eighty percent of subjects reporting sleep problems also reported problems with fatigue. Logistic regression analysis revealed the following: the more severe the brain injury the less likely the subject would be to have a sleep disturbance; subjects who had sleep disturbances were more likely to have problems with fatigue; females were more likely to have trouble with sleep. This study demonstrates the substantial prevalence of sleep disturbances after brain injury. It underscores the relationship between sleep disorders and perception of fatigue. It also underscores the need for clinicians to strive for interventional studies to look at the treatment of sleep and fatigue problems after brain injury.