The most common cause of drop-out from continuous ambulatory peritoneal dialysis (CAPD) therapy is an insufficient dose of dialysis. Several reports and the Dialysis Outcomes Quality Initiative (DOQI) guidelines recommend maintaining a weekly creatinine clearance (CCr) of at least 60 L/1.73 m2. Previously, at our center, we found that many patients switched from CAPD to hemodialysis (HD) owing to insufficient solute clearance (less than 50 L/1.73 m2). We attempted to determine whether once-weekly HD would improve solute clearance. We treated 7 cases (6 men, 1 woman; average age: 54.3 +/- 4.5 years; mean duration of CAPD: 4.3 +/- 1.1 years) with once-weekly HD therapy (3.5 hours; 200 mL/hour). The average CCr was 45 +/- 2 L/1.73 m2. No ultrafiltration failure was found. Addition of once-weekly HD therapy improved CCr to 66 +/- 7 L/1.73 m2. That improvement was attributable to not only to the addition of HD therapy but also to an increase in peritoneal CCr for 3 consecutive days after completion of once-weekly HD therapy. Creatinine clearance and ultrafiltration were both significantly increased. Other clinical parameters such as blood pressure control, weight control, and dose of erythropoietin were significantly improved after introduction of once-weekly HD therapy. Moreover, uremic symptoms such as pruritus and depression were markedly improved. In conclusion, once-weekly HD therapy in conjunction with regular CAPD therapy improves solute clearance and symptoms related to uremia in CAPD patients with an insufficient dialysis dose.