A common route for peritoneal infection is the bag transfer connecting site. To investigate possible reduction of such transfer infections with the use of a bag transfer set (UV-XD, Travenol, Baxter, Minneapolis), this study sampled patients using a transfer set with or without UV light sterilization. Calculations excluded peritonitis due to penetrating tunnel infection or defective peritoneal dialysis bag (4 episodes in 2 patients). The study included 51 patients with a median age of 62 years (range 25-81). Five were switched from manual connection (Travenol, Type II) to UV-XD, and each suffered from at least 2 peritonitis episodes during 9-24.5 months prior to the change to UV-XD. In this patient group, the incidence of peritonitis fell significantly from 1 peritonitis/4 to 1/21 months. The bag transfer set was used without UV light in 35 patients for a total of 178 months, producing an incidence of 1 episode/7.7 treatment months. These patients had significantly more peritonitis than 35 patients who used the UV light for a total of 416 months (1 episode/21 months). In 19 patients who used both techniques, there was less risk for peritonitis when UV light was used (p = 0.001). We conclude that the UV-XD device is simple to handle and may reduce the incidence of peritonitis, especially if the box is used in tandem with UV light sterilization.