To compare the incidence of catheter colonization and catheter-related bloodstream infections between heparin-coated catheters and those coated with a synergistic combination of chlorhexidine and silver sulfadiazine. Randomized, controlled clinical trial. A 20-bed medical-surgical intensive care unit. A total of 180 patients requiring the insertion of a trilumen central venous catheter. INTERVENTIONS. Patients were randomized to receive either a trilumen heparin or chlorhexidine and silver sulfadiazine-coated catheter. Catheter colonization was defined by a semiquantitative catheter tip culture yielding 15 or more colony-forming units or quantitative culture of 1,000 or more colony-forming units/ml. Catheter-related bloodstream infection as the isolation of the same microorganism from a peripheral blood culture and catheter tip. A total of 260 catheters were cultured. Out of 132 heparin-coated catheters, 29 were colonized and out of 128 chlorhexidine and silver sulfadiazine-coated catheters, 13 were colonized ( p=0.03), relative risk RR=2.16 (1.18-3.97). This represents an incidence of 23.5 and 11.5 episodes of catheter colonization per 1,000 catheter-days, respectively ( p=0.0059), RR=2.04 (1.05-3.84). Microorganisms isolated in catheter colonization from heparin-coated catheters were gram-positive cocci 23, gram-negative bacilli 7, and Candida spp 4. In chlorhexidine and silver sulfadiazine-coated catheters were gram-positive cocci 6 and gram-negative bacilli 11 ( p=0.009). The incidence of catheter-related bloodstream infections per 1,000 catheter-days was 3.24 in heparin-coated catheters and 2.6 in chlorhexidine and silver sulfadiazine-coated catheters ( p=0.79), RR=1.22 (0.27-5.43). In critically ill patients the use of trilumen central venous catheters coated with chlorhexidine and silver sulfadiazine reduced the risk of catheter colonization due to prevention of gram-positive cocci and Candida spp.