Aldosterone receptor blockers reduce cardiac-related morbidity and mortality. Recently, we demonstrated that long-term low-dose spironolactone is clinically safe in many hemodialysis (HD) patients. In the present study, we assess whether low-dose spironolactone treatment reduces the high incidence of cardio- and cerebrovascular (CCV) morbidity and mortality in HD patients. The investigators' hypothesis is that aldosterone receptor blockade by spironolactone reduces the risk of both CCV morbidity and death among HD patients.

Inclusion Criteria:

• Hemodialysis patients undergoing 4-hour-long HD thrice a week for at least 2 years
• With an average serum potassium level (immediately before dialysis on the first day of the week) of <6.5 mEq/l over the previous 2 months
• With a 24-hour urine output of <500 ml

Exclusion Criteria:

• A history of noncompliance
• Unstable vascular access
• Hypotension
• Hepatic failure
• Active cancer
• Any life-threatening disease other than ESRD