Sleep disorders are common in patients with end-stage renal disease (ESRD). The prevalence of sleep apnea is 10 times greater in patients with ESRD than in the general population. Although sleep apnea is not improved by conventional modes of dialysis, it is corrected by nocturnal hemodialysis, which provides a new and unique model to study its pathophysiology in this patient population. In addition to causing sleep disruption and impairment of daytime function, sleep apnea may also increase the cardiovascular morbidity and mortality that is commonly found in patients with ESRD. "Pathological" daytime sleepiness is found in 50% of patients with ESRD. Although its pathogenesis has been related both to sleep apnea and periodic limb movements, it has also been attributed to a variety of metabolic factors, including the severity of uremia. Further research is required to evaluate the impact of sleep disorders on the clinical outcome of patients with ESRD.