BACKGROUND The efficacy of combined diuretic treatment in patients undergoing continuous ambulatory peritoneal dialysis (CAPD) is not known. METHODS In a single-center, double-blinded, randomized controlled trial, we randomly assigned 51 adult CAPD patients to receive furosemide 1,000 mg/day, hydrochlorothiazide 100 mg/day, and spironolactone 50 mg/day (triple diuretics [TD] group) or furosemide 1,000 mg/day plus placebo (single diuretic [SD] group) for 6 months. The primary outcome was the difference in daily urine output at the 3rd and 6th month of the study compared to baseline (ΔUO) between the SD and TD group. Secondary outcomes were urinary sodium (UNa) and potassium (UK) excretion and overhydration (OH) measured by bioimpedance at 3 and 6 months compared to baseline (ΔUNa, ΔUK, and ΔOH, respectively) and daily glucose exposure (g/day). RESULTS Forty-three of 51 patients completed the 6-month trial. The ΔUO at 3 and 6 months was significantly higher in the TD group compared to the SD group (386.32 ± 733.92 mL/day vs. -136.25 ± 629.08 mL/day, P < 0.001, at 3 months; 311.58 ± 640.31 mL/day vs. 120.00 ± 624.07 mL/day, P < 0.001, at 6 months) but there was no significant difference in ΔUNa and ΔUK excretion. Hydration status was significantly better in the TD group (ΔOH 1.84 ± 2.27 L vs. 0.44 ± 1.62 L, P = 0.03, at 3 months; 1.49 ± 2.82 L vs. -0.48 ± 2.61 L, P = 0.02, at 6 months). There was no serious adverse event in this study. CONCLUSIONS For end-stage renal disease patients on CAPD, the combination of furosemide, hydrochlorothiazide, and spironolactone results in higher urine output and better volume control compared to furosemide alone.