Objective: To examine the rate of success and complications of Doppler-guided subclavian vein catheter insertion compared with standard insertion in patients considered at high risk for failure. Design: Prospective, randomized, crossover trial. Setting: University-affiliated tertiary care medical center. Patients: Two hundred forty patients were enrolled in the study. Patients were stratified for 3 known risk factors: (1) prior surgery in the subclavian vein region, (2) prior radiotherapy at the attempted catheterization site, and (3) an abnormal weight-height ratio. Interventions: Subclavian vein catheterization was performed either in standard or Doppler-guided fashion using the Smart Needle (Peripheral Systems Group, Mountain View, Calif), which is a Doppler probe at the tip of a cannulating needle. If subclavian vein catheterization was unsuccessful after 2 attempts, patients were crossed over to the other technique. Main Outcome Measure: Successful cannulation of the subclavian vein. Results: The success rate, either as an initial technique or as a technique, and complication rate were not significantly different with use of the Smart Needle. A subgroup of physicians had a significantly lower success rate using the Smart Needle. Conclusions: Doppler guidance did not increase the success rate or decrease the complication rate of subclavian vein catheterization when compared with the standard technique in high-risk patients. Doppler guidance was not more useful than the standard technique as a salvage technique following a previous failure of catheterization. Furthermore, real-time Doppler guidance of subclavian vein catheterization is a technique that is highly operator dependent.