The presence of an intraductal component together with an invasive carcinoma is known to be associated with a higher rate of local recurrence. The results of reviewing 250 resected surgical specimens from patients with breast cancer are reported. Two-hundred and fifty mastectomy specimens of invasive breast cancer were retrospectively analysed in order to determine intraductal components within the primary tumour as well as additional foci. In addition to the invasive carcinoma, a ductal carcinoma in situ (DCIS) of varying extent was identified in 127 instances. The intraductal components were marginal in 27.6% of the cases, extensive in 61.4%, and predominant in 11.0%. In addition, 21 patients had isolated DCIS only. Such in situ components were more frequently found in the age group younger than 41 years and in premenopausal patients. Seventeen percent of carcinomas associated with an intraductal component were multicentric in location as opposed to only 5% of the breast lesions without an intraductal component. The highest proportion of residual tumour was seen in poorly differentiated invasive carcinomas with DCIS. Intraductal carcinomas with intraductal component tended to have a higher incidence of a positive surgical margin. Small carcinomas with an extensive in situ component require careful surgical management in order to achieve a tumour-free margin.