Objective: To standardize the intravascular ultrasound (IVUS) analysis of coronary bifurcations. Background: Percutaneous treatment of bifurcation lesions is difficult particularly at the side branch ostium. Imaging techniques may improve our understanding of treatment options. There is no established IVUS methodology to assess the bifurcation. The present study aims to develop standards for bifurcation imaging. Methods: Quantitative IVUS analysis and 3D bifurcation angle measurements were performed in 34 patients who were selected from the Washington Hospital Center Database. Patients were included if both left anterior descending (LAD) and first diagonal (DX) pullbacks in the same procedure were done. Angiograms were available in 27 patients to measure the 3D bifurcation angle using specialized software. Pullbacks were analyzed proximal and distal to the bifurcation, and at the bifurcation. Results: Prox LAD versus Prox LAD(DX) were similar for vessel area (15.5 6 4.6 mm 2 vs. 15.9 6 4.0 mm 2 , P 5 0.19), lumen area (8.3 6 3.6 mm 2 vs. 8.6 6 3.3 mm 2 , P 5 0.25), and plaque area (7.2 6 2.0 mm 2 vs. 7.3 6 1.9 mm 2 , P 5 0.55). However, Bifurcation LAD was larger than Bifurcation DX for vessel area (17.3 6 4.0 mm 2 vs. 16.6 6 3.9 mm 2 , P 5 0.0083). The 3D angiographic bifurcation angle was 508 6 138 (range of 268-848), and did not affect the IVUS measurements. IVUS analysis showed that bifurcation lesions did obey Murray's Law, as Prox LAD lumen area measured 36.7 6 25.1 mm 3 versus Dist LAD /Dist DX measured 38.0 6 29.1 mm 3 , P 5 0.56. Conclusions: Two IVUS pullbacks should be performed for a complete assessment of the bifurcation and comparison with Murray's Law. The proposed IVUS analysis was not influenced by the bifurcation angle. ' 2009 Wiley-Liss, Inc.