Ductal carcinoma in situ has become clinically important with the advent of the rautine use of high quality mammography in western country. Literally, DCIS represent 15 to 20% of newly detected cases of breast cancer. At least half of these patients have treatment options other than conventional modified radical mastectomy, i.e. breast conserving surgery with radiotherapy. To determine clinical and histopathologic characteristics, the outcomes of 51 women with ductal carcinoma in situ treated at KCCH between l983 and 1993 are studied ret- rospectively. The results were as fo11ows; 1)The incidence of DCIS was 2.1%(51/2333) 2)The incidence of DCIS during 1980s was 2.0%, and 2.9% during 1990s. 3)The mean age of DCIS was 44.4 years old and peak age group was the 5th decade. 4)The most common clinical manifestation was a mass, followed by nipple discharge, Paget's disease, and pain in order. 5)The tumor size less than 2cm was the most common(26 out of 51 cases). 6)Cribriform type was the most common(15/51) and comedo-form represents 17.6%(9/51) of DCIS. 7)The ER positivity of DCIS was 70%(14/20). 8)Author experienced only one case of systemic recurrence at 24 months after modified radical mastectomy and at last she died 5 years after operation. Authors could not conclude the prognostic significance of DCIS according to the subtypes of DCIS or treatment modalities because of a little number of cases and a short term follow-up period. In conclusion, the incidence of DCIS in this study is not so high as in western countries, however for earlier detection of DCIS, it is better to make a screening mammography at least 2-years interval for women older than forty years old. Conservative procedures as an operative option may be considered in selected cases of DCIS.