The most serious problem related to the use of tunneled catheters in hemodialysis is bacteremia. The aim of this study was to detect hemodialysis catheter colonization and, establish a preemptive therapy based on a catheter antibiotic lock in order to prevent development of catheter-related bloodstream infections. During a 24-month period, all patients with tunneled catheters in our hemodialysis unit were evaluated by extracting a through-catheter leukocyte culture every 15 days.There were 28 episodes of catheter colonization occurring in 13 patients (2.2 colonization episodes per 1000 catheter patient-days). At the time of colonization, catheters had been in place for a mean of 562 days (range: 16 to 1475 days). Coagulase negative staphylococci (CNS) were the most common microorganisms to be isolated. A preemptive therapy consisting in teicoplanin locks (10 mg/mL) for 21 days was able to eradicate catheter colonization in 89% of the cases when CNS were isolated. However, relapse of colonization occurred in 61.2% of these cases. The mean duration of catheter use was 239 days (range: 9 to 483 days) after treatment of a colonization episode. The incidence of catheter-related bloodstream infection in our population was 0.78 episodes per 1000 catheter patient-days (IC 95%: 0.374-1.434). This study shows the utility of intra-catheter leukocyte culture for early detection of hemodialysis catheter colonization. Moreover, it establishes that the eradication of biofilm-related CNS is possible without the removal of the catheter, thus enabling a longer catheter lifespan.