Complete tumour excision in breast conserving surgery (BCS) is critical for successful outcome; involved circumferential resection margins are associated with increased disease recurrence. However, the importance of an involved anterior margin (IAM) is less clear. The purpose of this study was to review an aggressive approach to IAM and hence assess whether anterior margin re-excision (RE) yields clinical benefit.A review of prospectively collected clinical and pathology data was performed for all patients who underwent BCS between 2006 and 2010 through a single cancer centre. An involved margin was defined as < 1 mm clearance of invasive or in-situ breast cancer.1667 patients underwent BCS for invasive and/or in-situ disease, of whom 114 underwent RE. A total of 170 involved margins were identified: most commonly the anterior (52 margins) followed by the posterior (39 margins) and inferior (31 margins) margin. Patients with IAM were more likely to have grade 3 invasive disease (p = 0.0323) but less likely to have residual disease found at re-excision (2/49 vs. 32/101 margins, p = 0.0033); there were no differences when in-situ characteristics were compared.RE of IAM after BCS rarely yields further disease; multi-disciplinary teams should consider whether further therapy for an IAM is required on a patient by patient basis.