The automatic release of povidone iodine (PVP-I) into the outlet tube of a urinary collecting bag significantly reduced urinary tract infections (UTIs) and provided a more practical bacterial barrier than manual instillation of PVP-I into the bag as used previously. In 52 patients using a new urinary drainage system with a cartridge that released PVP-I into the outlet tube of the collection bag UTIs developed in 3, compared with 57 patients using a standard closed drainage system and in whom 13 UTIs developed (p less than 0.005). The PVP-I group had 92 percent of the accumulative catheter-days free of bladder infection, compared with 77 percent in the standard group. The main route of bacterial contamination leading to urinary drainage UTIs was through the collection bag.