Previous studies of various brands of polyurethane dressings have noted differences in the rates of catheter colonization. We compared Bioclusive transparent polyurethane (TP) dressing with a cotton gauze (CG) dressing on peripheral intravenous (IV) access sites for the incidence of phlebitis, catheter tip colonization, skin colonization, and catheter-related bacteremia. The study, involving 598 ward patients, was case controlled, prospective, and randomized for a period of 4 months. Each patient was entered into the study only once, and all dressings were applied by a member of the IV therapy team. No significant difference was seen for phlebitis rate (TP: 9.8% vs. CG: 7.6%) or catheter tip colonization, defined as greater than 15 colony forming units (CFU) (5.7% vs. 4.4%) by a semiquantitative technique. Cultures of specimens from the skin and catheter tips of the majority of patients (91%) showed no growth. An association was found between those patients with greater than 15 CFU isolated from catheter tips and those with phlebitis (p = 0.022). No documented catheter-related bacteremia occurred in either study group.