Peritoneal dialysis (PD) is the first-line treatment of end stage renal disease (ESRD) in Hong Kong. Despite the advances in antibiotic therapy and connecting system, recurrent peritonitis remains the major cause of peritoneal failure. A recent study showed that an elevated bacterial DNA fragment levels in PD effluent 5 days prior to the completion of antibiotics predicts the development of relapsing or recurrent peritonitis episodes. We hypothesize that prolonged antibiotic therapy in PD patients with peritonitis and high PD effluent bacterial DNA fragment levels could prevent the development of relapsing and recurrent peritonitis. We plan to conduct a randomized control study of 360 patients with PD peritonitis. After inform consent, they will be randomized to receive one additional week of the effective antibiotic treatment (the Preemptive Treatment Group) or no additional treatment (the Control Group). Specimens of PD effluent will be collected 5 days prior to the completion of antibiotics for the measurement of bacterial DNA fragments. All patients will be followed for 6 months after completion of antibiotic therapy for the development of relapsing, recurrent, or repeat peritonitis episodes. Our study will determine the efficacy of a test-before-treat algorithm that could reduce the incidence of relapsing and recurrent peritonitis and, at the same time, minimize the unnecessary use of prolonged antibiotic treatment.