The optimal management of ductal carcinoma in situ of the breast is controversial. With the introduction of the National Mammographic Breast Screening Programme the condition will be encountered more frequently. We have reviewed 76 patients from a 12-year period treated by one surgeon (R.W.B.) at the Nottingham City Hospital. Fifty-nine patients had either ductal carcinoma in situ or lobular carcinoma in situ; 17 patients had Paget's disease. The mean age at diagnosis was 54 years and the commonest mode of presentation was with a palpable breast lump. Pre-operative mammography was performed in 31 patients with ductal carcinoma in situ and 28 were reported as showing malignancy. Patients with a lesion in the breast parenchyma were treated either by mastectomy (simple, subcutaneous or 'wedge'--see text) or by lumpectomy and radiotherapy. Patients with Paget's disease were treated by simple mastectomy, wedge mastectomy or a cone excision of the nipple and underlying tissue. The mean follow-up period was 65 months. Patients treated by any of the procedures less than simple mastectomy had a significant chance of developing local recurrence. A detailed histological review was made and grade, microinvasion, calcification, necrosis and completeness of excision were assessed for each tumour. None of these factors was correlated with subsequent local recurrence.