BACKGROUND: The aim of this study was to evaluate the influence of operative experience in obtaining tumor-free margins in breast-conserving therapy. In the case of palpable breast cancers, lumpectomies can safely be performed by any surgical resident. For nonpalpable breast cancers, lumpectomies should be treated only by senior residents or attending surgeons, even if supervision during the operation is given by an attending surgeon for junior residents. Radicality of breast carcinoma excision, defined by the tumor-free margin of the removed specimen has been determined to be the major prognostic factor for local recurrence. The aim of this study was to evaluate the influence of operative experience in obtaining tumor-free margins in breast-conserving therapy (BCT). Can lumpectomy for breast carcinoma be performed by surgical residents safely? METHODS: All lumpectomies for breast carcinoma between 1999 and 2003 were included out of a prospective database of a single institution. Radicality of resection and patient and histopathologic tumor characteristics were analyzed for 660 lumpectomies. Operative experience of the surgeon performing the lumpectomy was staged as junior residents (JR, years 1-3 in residency), senior residents (SR; years 4-6 in residency), and attending surgeon (AS). RESULTS: A significant difference in obtaining tumor-free margins for palpable tumors was found between ASs (81%) vs. SRs assisted by another resident (92%). For nonpalpable tumors, a significant difference was found in two groups: (1) SRs assisted by another surgical resident (86%) vs. JRs assisted by another surgical resident (61%) and (2) ASs (83%) vs. JRs assisted by another resident (61%) or assisted by an AS (73%). CONCLUSION: Surgical residents can safely perform BCT in patients with palpable breast cancer. The level of experience has no statistical significance for palpable tumors in a high-volume center. Nonpalpable lesions should be treated only by SRs or ASs.