PURPOSE/OBJECTIVES To review the state of the science on sleep/wake disturbances in people with cancer and their caregivers. DATA SOURCES Published articles, books and book chapters, conference proceedings, and MEDLINE, the Cumulative Index to Nursing and Allied Health Literature, PsycINFO, and the Cochrane Library computerized databases. DATA SYNTHESIS Scientists have initiated studies on the prevalence of sleep/wake disturbances and the etiology of sleep disturbances specific to cancer. Measurement has been limited by lack of clear definitions of sleep/wake variables, use of a variety of instruments, and inconsistent reporting of sleep parameters. Findings related to use of nonpharmacologic interventions were limited to 20 studies, and the quality of the evidence remains poor. Few pharmacologic approaches have been studied, and evidence for use of herbal and complementary supplements is almost nonexistent. CONCLUSIONS Current knowledge indicates that sleep/wake disturbances are prevalent in cancer populations. Few instruments have been validated in this population. Nonpharmacologic interventions show positive outcomes, but design issues and small samples limit generalizability. Little is known regarding use of pharmacologic and herbal and complementary supplements and potential adverse outcomes or interactions with cancer therapies. IMPLICATIONS FOR NURSING All patients and caregivers need initial and ongoing screening for sleep/wake disturbances. When disturbed sleep/wakefulness is evident, further assessment and treatment are warranted. Nursing educational programs should include content regarding healthy and disrupted sleep/wake patterns. Research on sleep/wake disturbances in people with cancer should have high priority.