OBJECTIVE To compare relative efficacies and complications associated with the use of double lumen vs. single lumen umbilical venous catheters in critically ill neonates. METHODS Prospective randomized control trial. METHODS Neonatal ICU. METHODS Forty-three critically ill neonates. METHODS Group 1 patients (n = 20) received single lumen umbilical venous catheters and group 2 patients (n = 23) received double lumen catheters. A record of the following information was kept: demographic data including diagnosis and indication for umbilical venous catheter insertion, catheter tip location, length of catheterization (days), number of additional iv catheters and complications (sepsis, hepatic necrosis, thrombosis, or mechanical complications). RESULTS Double lumen umbilical venous catheters were well tolerated and were associated with no significant increased risk of mechanical complications when compared with single lumen umbilical venous catheters. The number of additional iv catheters required (0.8 +/- 0.1 [SD]) was significantly (p less than .05) less in the double lumen umbilical venous catheter group as compared with additional iv catheters required (2.3 +/- 0.8) in the single lumen umbilical venous catheter group. CONCLUSIONS Double lumen umbilical venous catheters are well tolerated for short-term use, decrease the need for additional venous catheters in critically ill neonates, and may not significantly increase the risk of mechanical complications when compared with single lumen umbilical venous catheters.