PURPOSE OF REVIEW: We herein summarize the current evidence on the clinical outcome associated with the use of single and multiple arterial grafts for coronary bypass surgery and the role and importance of the Randomized comparison of the clinical Outcome of single versus Multiple Arterial grafts (ROMA) trial. RECENT FINDINGS: Observational evidence suggests that the use of multiple arterial grafts is associated with better clinical outcomes compared to the use of a single arterial graft. Randomized evidence is inconclusive; the 5-year interim analysis of the largest randomized trial on the topic did not show any clinical benefit associated with the use of bilateral versus single internal thoracic arteries, whereas a pooled analysis of the trials comparing the radial artery and the saphenous vein as a second graft showed a significant reduction in follow-up cardiac events using the radial artery. Hidden confounders and treatment allocation biases as well as methodological flaws are the most likely explanation of this contradiction. SUMMARY: ROMA was conceived based on the lessons learned from a critical analysis of the existing randomized and observational evidence with the aim to provide a definitive answer to the question of the potential clinical benefit of multiple arterial grafts for coronary bypass.