Although twin-bag disconnect fluid-transfer systems for continuous ambulatory peritoneal dialysis (CAPD) have a lower rate of catheter-related infection than single-bag systems, their greater monetary purchase cost has prevented universal adoption. Therefore, a single-center randomized study was performed in 63 adult patients to compare the efficiency and total cost of Freeline Solo (FS, twin-bag) and Basic Y (BY, single-bag) systems. Patients were new to CAPD (N = 39), or had a new CAPD catheter, or had had no episodes of peritonitis or exit-site infection in the previous 12 months (N = 24). Total follow-up was 631 patient months (pt.mon), and 53 patients were still on the trial at its termination. Patients rated FS as easier to use than BY (P < 0.001). Peritonitis occurred on 23 occasions in 12 out of 30 patients using BY, and on seven occasions in five of 33 patients using FS. Time to first infection was less with BY than FS (hazard ratio, 2.4; 95% confidence interval (CI), 1.0 to 5.3; P < 0.04). Cumulative incidence of peritonitis was 1 per 14.0 pt.mon with BY and 1 per 46.5 pt.mon with FS (odds ratio, 3.6; 95% CI 1.5 to 8.5; P = 0.004). Length of hospitalization for peritonitis or exit-site infection was 98 days in six patients with BY, versus 17 days in two patients with FS. With BY, four catheters were removed because of infection, but none with FS (P < 0.05). With BY, the total cost of infection was $AUD127,079 ($5033 per pt.yr) versus $19,250 ($704 per pt.yr) with FS, which offset the higher purchase cost of FS. The total cost of CAPD was $AUD956 per pt.yr less with FS than BY. In conclusion, the higher purchase cost of the FS twin-bag system is more than offset by savings from its lower incidence of peritonitis.