Ductal carcinomas in situ (DCIS) are sometimes treated too aggressively by surgery. We discuss minimal invasive surgery for DCIS on the basis of our experience at the Cancer Institute Hospital in Tokyo.We performed surgery for 667 cases of DCIS between 1987 to 1998. This twelve year period we divided into three periods; 1987-1990,1991-1994, and 1995-1998.DCIS comprised 10% of all breast cancers, and tended to increase in incidence over time. The number of minimally invasive procedures such as breast conserving treatment (BCT), surgery without axillary dissection, and day surgery increased in later periods. In BCT for DCIS the surgical margin status is the most important factor, the rate of negative surgical margins was higher in DCIS than invasive cancer, and especially high in cases of mammographically detected nonpalpable cancer, the incidence of which is increasing yearly. The outcome of the 667 cases was very good. No distant metastases were observed, and the incidence of ipsilateral breast cancer(including second primary cancer) in these cases was 5%Because small cancers, including nonpalpable cases, will be detected more frequently, minimal invasive surgery will become more common for DCIS.