Sickle cell disease (SCD), a group of genetic disorders characterized by the predominance of abnormal hemoglobin S, results in severe anemia and vaso-occlusion leading to progressive organ damage. These events, in turn, are responsible for multiple comorbidities in SCD. Neurobehavioral (cognitive and behavioral) deficits and progressive neurobehavioral decline are among the most pervasive comorbidities of SCD, and begin in early childhood. These deficits contribute to poor academic performance and social problems, and may ultimately lead to occupational restriction and limitations on adult achievement of independence. Little is known about the risk to neurobehavioral functioning posed by disturbed sleep and sleep-disordered breathing in these children. Evidence from studies of children without SCD suggests that several aspects of disordered sleep, including inadequate and fragmented sleep, snoring and obstructive sleep apnea (OSA) contribute to neurobehavioral impairment. The risks posed by disordered sleep might be even greater in children with SCD, given the underlying vulnerability to poor neurobehavioral outcomes posed by their sickling disorder. To begin addressing our limited understanding of the possible risk for neurobehavioral impairment imposed by disturbed or disordered sleep, this study aims to describe sleep in a sample of children with SCD referred for neurobehavioral evaluation for academic and cognitive difficulties. We will further explore the association of sleep disturbance and sleep-disordered breathing with neurobehavioral test scores. We propose to evaluate sleep in 25 children aged 5-18 years who have undergone comprehensive neurodevelopmental or neuropsychological assessment within the past 5 years. We will collect parent- and child-report of sleep hygiene, sleep habits and sleep disordered breathing using validated questionnaires and one week of actigraphy to objectively measure sleep patterns (total sleep time and sleep fragmentation). We hypothesize that neurobehavioral deficits, particularly full-scale IQ and measures of executive function are associated with several sleep variables, particularly total sleep time and sleep fragmentation (arousals and awakenings), as well as sleep-disordered breathing. Discovery of associations between sleep disturbances or sleep-disordered breathing and general or specific areas of neurobehavioral functioning would provide targets for interventions to improve sleep and correct sleep-disordered breathing, thereby improving long-term neurobehavioral outcomes.