Interdialytic hemodialysis catheter-locking solutions could contribute to a reduction of catheter-related complications, especially infections. However, they can cause side effects because of leakage from the tip of the catheter. Recently, trisodium citrate (TSC) has been advocated because of its antimicrobial properties and local anticoagulation. In a multicenter, double-blind, randomized, controlled trial, TSC 30% was compared with unfractionated heparin 5000 U/ml for prevention of catheter-related infections, thrombosis, and bleeding complications. The study was stopped prematurely because of a difference in catheter-related bacteremia (CRB; P < 0.01). Of 363 eligible patients, 291 could be randomized. The study included 98 tunneled cuffed catheters and 193 untunneled. There were no significant differences in patient and catheter characteristics on inclusion. In the heparin group, 46% of catheters had to be removed because of any complication compared with 28% in the TSC group (P = 0.005). CRB rates were 1.1 per 1000 catheter-days for TSC versus 4.1 in the heparin group (P < 0.001). For tunneled cuffed catheters, the risk reduction for CRB was 87% (P < 0.001) and for untunneled catheters was 64% (P = 0.05). Fewer patients died from CRB in the TSC group (0 versus 5; P = 0.028). There were no differences in catheter flow problems and thrombosis (P = 0.75). No serious adverse events were encountered. Major bleeding episodes were significantly lower in the TSC group (P = 0.010). TSC 30% improves overall patency rates and reduces catheter-related infections and major bleeding episodes for both tunneled and untunneled hemodialysis catheters. Flow problems are not reduced.