Intraductal carcinoma of the breast (DCIS), by definition, cannot give axillary metastases. Axillary dissection is therefore not indicated. The role of the sentinel lymph node (SLN) biopsy in the management of DCIS has not yet been established. A 6-13% risk of SLN involvement is reported in Literature. The aim of the present study is to assess the role of SLN biopsy in patients with pure DCIS and attempt to identify guidelines for routine practice in managing such patients. From March 1996 to December 2003, 508 consecutive patients with pure DCIS of the breast underwent SLN biopsy at the European Institute of Oncology in Milan. Clinical and pathological data were prospectively collected. In all cases of previous surgery or stereotactic biopsy performed elsewhere all pathological slides were reviewed. Cases with microinvasion were excluded from this investigation. Lymphatic mapping was performed using a radiocolloid technique. Most of the patients underwent conservative surgery and removal of the SLN which was sent for conclusive histology. SLN metastases were detected in 9 out of 508 (1.8%) patients. In five patients only micrometastasis (<2 mm) was detected. Eight patients underwent complete axillary dissection. In none of these patients did we find additional positive axillary lymph nodes. In conclusion, due to the low prevalence of metastatic involvement (1.8%), SLNB should not be considered a standard procedure in the treatment of all patients with DCIS. In pure non-comedo DCIS completely excised by radical surgery with free margins of resection SLNB should be avoided since not only it is unnecessary but could also jeopardize a successive re-SLNB in case of invasive recurrence. A very extensive and accurate histological examination of the tumour in DCIS is compulsory to exclude micro-invasive foci and, finally, to decrease the prevalence of unexpected SLN metastases. SLNB should be considered in case of DCIS where there exists a strong doubt of invasion at the definitive histology, such as large solid tumours or diffuse or pluricentric microcalcifications undergoing mastectomy. Moreover, if the trend is statistically confirmed with a wider population, large comedo-DCIS, presenting superior risk of SLNs metastasis, could be scheduled for SLNB. If the SLN is micrometastatic complete axillary dissection is not unavoidable.