In patients with end-stage renal disease, nervous system dysfunction remains a major cause of disability. Patients with chronic renal failure who have not yet received dialysis may have symptoms ranging from mild sensorial clouding to delirium and coma. Dialysis itself is associated with at least three distinct disorders of the central nervous system, including the dialysis disequilibrium syndrome, dialysis dementia, and progressive intellectual dysfunction. Peripheral neuropathy is also a major cause of disability in uremic patients. Aluminum probably contributes to the pathogenesis of dialysis dementia. Parathyroid hormone, the levels of which are elevated in patients with renal failure, also may be a uremic neurotoxin. Biochemically, brain calcium levels are elevated in renal failure, possibly because of the action of parathyroid hormone. Studies on synaptosomes have also shown that parathyroid hormone can affect calcium transport in the brain. Intellectual dysfunction, dialysis dementia, uremic neuropathy, and the dialysis disequilibrium syndrome can be diagnosed when the characteristic clinical findings are present and other causes of nervous system dysfunction have been excluded.