The role of cavity shaves in reducing re-excision rates in breast conserving surgery (BCS) remains unclear. We compared rates of close margins and re-excision following cavity shaves based on either intraoperative radiology or systematic cavity shaves. Data was recorded prospectively from 1999 to 2003 for 217 patients undergoing BCS. For the first 106 cases, cavity shaves were performed when intraoperative radiological margins appeared close (<10 mm). The remaining 111 cases had systematic superior and inferior cavity shaves (SSICS). Close margins and re-excision rates were compared between groups. The median weight of excised tissue was less in group two: 82.8 g versus 100.5 g, P=0.001. SSICS reduced close margins by 83% (18/106 versus 8/111), OR 0.17, 95% CI 0.08-0.48, P=0.001. Multivariate analysis showed SSICS also reduced re-excision rates (15 versus 8 cases), OR 0.26, 95% CI 0.09-0.74, P=0.012. SSICS reduces close margins and re-excision rates. This approach has additional cosmetic benefits because less tissue is excised.