Hypokalemia is a common problem in patients on continuous ambulatory peritoneal dialysis (CAPD). We evaluated the efficacy and safety of spironolactone in CAPD patients with hypokalemia. We reviewed the clinical response of 12 consecutive hypokalemic CAPD patients treated with spironolactone in our dialysis center. All patients received spironolactone 25 mg daily. There was no significant change in the serum potassium level after administration of spironolactone (3.30 ± 0.26 vs. 3.46 ± 0.38 mmol/L, p = 0.28), even though three patients required regular oral potassium supplementation. There was also no significant change in arterial blood pressure or urine output after spironolactone treatment. Spironolactone was well tolerated and no hyperkalemia was recorded. Spironolactone is not effective in the treatment of hypokalemia in stable CAPD patients, but the agent is well tolerated, at least in CAPD patients with little residual renal function. Future studies are warranted to determine the therapeutic role of spironolactone in CAPD patients with concomitant congestive heart failure or cardiovascular disease.