The high burden of cognitive impairment in hemodialysis and chronic kidney disease (CKD) patients has only recently become recognized. Up to 70% of hemodialysis patients aged 55 years and older have moderate to severe chronic cognitive impairment, yet it is largely undiagnosed. Recent studies describe the strong graded relation between estimated glomerular filtration rate and cognitive function in CKD patients. The process of conventional hemodialysis may induce recurrent episodes of acute cerebral ischemia, which, in turn, may contribute to acute decline in cognitive function during dialysis. Thus, the worst time to communicate with dialysis patients may be during the hemodialysis session. Both symptomatic and occult, subclinical ischemic cerebrovascular disease appears to play a large role in a proposed model of accelerated vascular cognitive impairment in these populations. Severe cognitive impairment or dementia among hemodialysis patients is associated with an approximately 2-fold increased risk of both mortality and dialysis withdrawal. Predialysis cognitive screening and adding dementia to the list of comorbidities on Form 2728 would provide critical information regarding the benefit versus risks of receiving dialysis. It could also improve quality of care and outcomes by raising clinicians' awareness of the potential effects of cognitive impairment on medication, fluid, and dietary compliance and the ability to make advance directive decisions among dialysis patients. Although much remains to be learned regarding the pathophysiology of cognitive impairment in kidney disease, the public health implications of this substantial burden are immediate.