Sentinel node (SN) biopsy technique has been reported to be a very accurate staging procedure in patients with stage I/II melanoma. Whether it is as accurate in patients with breast cancer has to be studied more extensively. Eighty-three patients with clinically T1-T2 N0M0 breast cancer were peri-tumorally injected with 99m-Tc colloidal-albumin. Lymphoscintigraphy was performed either 4 or 18 h after the injection. Using a gamma probe the SN were located in vivo, removed from the axillary specimen and sent for histological examination. No focal accumulation was seen on the lymphoscintigraphy in 17 patients. Two patients had parasternal SN locations only and in seven patients the localization of the SN failed. Of the remaining 57 patients, 23 had positive axillary basins, of which 22 were correctly predicted by one or more positive SN. There was one false-negative biopsy (sensitivity=96%). In 12 of the 22 positive axillary basins, SN was the only positive node. We conclude that the SN biopsy technique is a promising and feasible procedure in about three-quarters of patients with clinically T1-T2 N0M0 breast cancer. However, more data are needed to establish the actual sensitivity of this procedure.