Purpose: Tunneled catheters used for hemodialysis treatment often become dysfunctional due to deposition of clotting material within the catheter lumen. In a retrospective study design we investigated the effect of mechanical brushing of dysfunctional tunneled catheters using a metal guide wire with simultaneous installation of urokinase. Materials and Methods: During a period of 26 months all together 24 different catheters in 21 chronic hemodialysis patients were brushed due to insufficient blood flow or increased arterial or venous line pressures resulting in repeated alarms during dialysis treatments. Results: Median functional survival after brushing was 45 days with 8 catheters being exchanged (n=5) or rebrushed (n=3) within 10 dialysis sessions (4 weeks). After 2 months all together 13 (54%) catheters were exchanged due to repeated dysfunction and by 3 months functional survival was only about 35%. The catheters needing exchange were characterized by low flow and high arterial line resistance already in the dialysis sessions immediately following the brushing procedure. Median survival of the exchanged catheters was considerably longer (>400 days) as compared to the brushed catheters. Conclusions: In conclusion mechanical brushing of dysfunctional tunneled hemodialysis catheters can prolong short term function but only affects long term catheter survival in a minority of the patients.