Peritoneal dialysis (PD) is recommended as first-line renal replacement therapy for end-stage renal disease. Combined therapy with PD and hemodialysis (HD) is an option for patients on PD with inadequate dialysis and/or fluid overload that has rapidly gained popularity in Japan. The clinical benefits of combined therapy have been recognized. After switching from PD alone to combined therapy, there is a decrease in body weight, blood pressure, and serum creatinine, as well as an increase in the hemoglobin level, suggesting significant improvement in dialysis and decreased fluid overload. Further, there is a decrease in the dialysate-to-plasma ratio of creatinine, which is obtained from the peritoneal equilibration test and is known to be an independent risk factor for encapsulating peritoneal sclerosis, suggesting improved functioning of the peritoneal membrane. Several studies found that survival in patients on combined therapy was similar to or better than that in patients on PD or HD. Key Messages: Combined therapy with PD and HD is becoming widespread in Japan; however, its clinical benefits, especially in terms of morbidity and mortality, have not been validated. Furthermore, no criteria for initiation or discontinuation of combined therapy have been established, mainly because the previously published studies have been retrospective, single-center studies with small sample sizes that performed before-and-after comparisons only. Prospective cohort studies are needed to validate the use of combined therapy with PD and HD.