Abstract Study objective To investigate the frequency of bacterial colonization of epidural catheters used for postoperative pain treatment longer than 24 hours in abdominal, thoracic, or trauma surgery patients. Design Retrospective study. Setting Intermediate care facility and general ward of a university hospital. Patients 502 patients who received epidural catheters after abdominal, thoracic, or vascular surgery at our institution from January 1996 to December 2000. Interventions Placement of an epidural catheter, which was used for postoperative pain treatment, for more than 24 hours. The puncture site dressing included saturation each day with povidone-iodine. Measurements and main results Microbiologic monitoring of epidural catheter tips and daily examination of puncture sites with regard to signs of inflammation took place. Four times daily patients were examined to check adequacy of pain treatment and neurologic deficits. Catheter tip cultures were positive in 29 patients (5.8%). Staphylococcus epidermidis was isolated in 22 cases (76%). No case of spinal epidural abscess was observed within 6 months after epidural catheterization. The average catheterization time was 5 days (quartile range: 4 to 6 days). Conclusions Meticulous management ensures a relatively low level of bacterial contamination in epidural catheters applied for postoperative pain treatment greater than 5 days. Contamination rarely leads to spinal epidural infection.