The increasingly frequent diagnosis of ductal carcinoma in situ (DCIS) presents a major clinical dilemma. Our inability to predict which DCIS will progress to invasive cancer or the time interval in which recurrent DCIS or invasive cancer will occur has resulted in treatments ranging from mastectomy to excision and observation being offered to patients. Four randomized trials have demonstrated that the use of radiation reduces the risk of local recurrence by about 50% in women with DCIS. Prospective attempts to duplicate retrospective findings that wide excision results in high rates of local control have been unsuccessful. Patient attitudes towards risks and benefits of treatment are an important component of treatment choice in the absence of predictors of biologic behavior.