Objectives: The aim of this study was to evaluate a new fully automated lumen border tracing system based on a novel multifrequency processing algorithm. Background: We developed the multifrequency processing method to enhance arterial lumen detection by exploiting the differential scattering characteristics of blood and arterial tissue. The implementation of the method can be integrated into current intravascular ultrasound (IVUS) hardware. Methods: This study was performed in vivo with conventional 40-MHz IVUS catheters (Atlantis SR Pro™, Boston Scientific Corp, Natick, MA) in 43 clinical patients with coronary artery disease. A total of 522 frames were randomly selected, and lumen areas were measured after automatically tracing lumen borders with the new tracing system and a commercially available tracing system (TraceAssist™) referred to as the “conventional tracing system.” The data assessed by the two automated systems were compared with the results of manual tracings by experienced IVUS analysts. Results: New automated lumen measurements showed better agreement with manual lumen area tracings compared with those of the conventional tracing system (correlation coefficient: 0.819 vs. 0.509). When compared against manual tracings, the new algorithm also demonstrated improved systematic error (mean difference: 0.13 vs. −1.02 mm2) and random variability (standard deviation of difference: 2.21 vs. 4.02 mm2) compared with the conventional tracing system. Conclusions: This preliminary study showed that the novel fully automated tracing system based on the multifrequency processing algorithm can provide more accurate lumen border detection than current automated tracing systems and thus, offer a more reliable quantitative evaluation of lumen geometry. © 2011 Wiley Periodicals, Inc.