The optimal margin in breast-conserving surgery is controversial, and re-excision is common. Pathologic margin assessment is not standardized, and tumor biology and the use of systemic therapy have a major impact on local control. A study-level meta-analysis found no difference in local recurrence for margin widths of 1, 2, and 5 mm, leading a multidisciplinary panel to recommend adoption of no ink on tumor as the standard definition of a negative margin. J. Surg. Oncol. 2014 110:2–7. © 2014 Wiley Periodicals, Inc.