PURPOSE: Screening mammography is now a widely used procedure and as result, the incidence of ductal carcinoma in situ (DCIS) of the breast is increasing. The purpose of this study was to investigate the incidence and clinicopathologic features of DCIS and to evaluated the difference of clinical characteristics between breast conserving surgery and mastectomy. METHODS: We reviewed the clinical record of 112 patients with DCIS, including those with microinvasion, who were treated at the Department of Surgery, Keimyung University Hospital from January 1992 to December 2005. RESULTS: The incidence of DCIS and microinvasive carcinoma was 8.0% of all the breast cancers. The most prevalent age was in the fifth decade and the mean age was 48.8 years old. An abnormality on routine health screening exams was the most common cause of detection. Preoperatively, the diagnostic methods were fine needle aspiration biopsy in 7.6%, core needle biopsy in 19.0%, needle localization open biopsy in 33.3% and excisional biopsy in 40.0%. The surgical procedures were modified radical mastectomy or simple mastectomy in 48.2% and a breast conservation procedure in 51.8%. The final surgical margin status showed a free margin in 83.0%, a close margin in 12.8%, and an involved margin in 4.3%. The hormonal receptor positive rate was 75.3% and the c-erbB-2 positive rate was 32.9%. The patient who received mastectomy had a larger tumor size, a more common presentation of microcalcification on MMG, a more frequent comedo type lesion and a lesser expression of hormonal receptor. There was no significant difference between the two groups in terms of the c-erbB-2 expression. CONCLUSION: The widespread use of screening mammography will increase the chance to detect DCIS, and conservative surgery will be performed more frequently in a selected group of these patients.