A controlled study in two centres compared the efficacy of the standard continuous ambulatory peritoneal dialysis (CAPD) system with that of a new method consisting of a Y-shaped set filled with sodium hypochlorite during the dwelling time. 62 new CAPD patients were randomly allocated to the standard method (group A: 30 patients; age 55.5 +/- 17.5 years) or to the Y-system (group B: 32 patients; age 55.1 +/- 14.3 years). In group A, there were 31 peritonitis episodes in 17 patients (57%) during a cumulative period of 351 months--1 episode every 11.3 patient-months. In group B, there were 11 peritonitis episodes in 10 patients (31%) during 363 months--1 episode every 33 patient-months. Life-table analysis showed a significant difference between the incidence of peritonitis in the two groups. The Y-system method is simple and economical and the frequency and the severity of side-effects appears to be acceptable.