Heparin and saline are commonly used to fill hemodialysis central venous catheters to prevent their thrombosis during the interdialytic period. The purpose of this prospective clinical study was to evaluate whether replacing heparin with citrate or polygeline could ensure satisfactory catheter function without exposing patients to the risk of systemic heparinization. Thirty end-stage renal disease (ESRD) patients with subclavian or jugular single lumen catheters as temporary vascular access for hemodialysis were enrolled. After the insertion of the catheters, the patients were randomly assigned to one of the following three filling groups: Group A, heparin; Group B, citrate; Group C, polygeline. Before each dialysis, the filling solution was aspirated and clot volume, if present, was measured. The catheter usage time and the clot volume were 23 +/- 24 days and 0.052 +/- 0.035 ml in Group A, 51 +/- 36 days and 0.059 +/- 0.032 ml in Group B, and 32 +/- 10 days and 0.056 +/- 0.038 ml in Group C, respectively. Our results indicate that citrate or polygeline can replace heparin effectively as a filling solution for single lumen temporary hemodialysis catheters.