Study objective: To compare the use of real-time-ultrasound guidance with the standard landmark-oriented approach for obtaining femoral vein catheterization in patients requiring intravenous access during CPR. Methods: Prospective, randomized, paired subject controlled clinical trial in the setting of an urban teaching county hospital emergency department. The study comprised a convenience sample of 20 patients presenting with apnea and pulselessness in the ED. Each patient received bilateral femoral lines, one by ultrasound guidance and one by the landmark approach (control). Randomization determined which technique and which side would be attempted first. The following parameters were recorded: time to initial flash of blood, time to completion of catheterization, number of needle passes, and rate of arterial catheterization. CPR and Advanced Cardiac Life Support protocols were continued during both procedures. Results: Real time ultrasound guided catheterization had a higher success rate (90% versus 65%, P=.058), a lower number of needle passes (2.3+3 versus 5.0+5, P=.0057), and a lower rate of arterial catheterization (0% versus 20%, P=.025) than the standard landmark oriented approach. Ultrasound was also slightly faster in time to blood flash and in time to catheterization. An incidental finding of interest was that real-time ultrasound demonstrated the presence of femoral vein pulsations during CPR. Conclusion: Real time ultrasound-guided femoral vein catheterization was faster and produced a lower rate of inadvertent arterial catheterization and a higher rate of success during CPR than the standard landmark oriented approach. Also, ultrasound demonstrated that palpable femoral pulsation during CPR is venous rather than arterial.