Purpose: to evaluate the use of intra-operative ultrasound (IOUS) in localization of breast lesions during breast conserving surgery (BCS) and correlate with pathological results for adequate negative margins. Introduction: breast conserving surgery (BCS) is an alternative to mastectomy in treatment of cancer breast. The matter of tumor localization is a problematic issue with the wire localization being the commonest with multiple drawbacks. Another method for localization which is the intra-operative sonography is investigated. Patients and methods: this prospective, controlled study enrolled 60 female patients. 30 patients comprised case group (group I) who undergone breast conserving surgeries with IOUS guidance and 30 patients as a control (group II) undergone breast conserving surgeries without IOUS guidance. Pathological microscopic examination of the specimen had been conducted to ensure adequate negative margins. Results: Only 6 patients of the case group had involved inadequate margins while 14 of the control group had inadequate margins. Conclusion: intra-operative ultrasound is an essential adjunct to surgery that should be experienced to obtain safety and cosmoses.