Axillary sentinel lymph node biopsy (SLNB) is widely used to identify the first lymph node draining breast tumors. When the sentinel lymph node is free of metastasis, axillary dissection is avoided because the rest of the nodes are expected to be negative as well. A false-negative rate of 5% is considered acceptable. In the case of a false-negative SLNB, adjuvant local and systemic treatments might be suboptimal. We assessed the effect of intraoperative axillary palpation for clinically suspicious lymph nodes that are not otherwise detected by radioactive tracer or blue dye on the false-negative rate of SLNB in breast cancer patients. Our prospective database of patients having surgery for primary invasive breast cancer and who had a SLNB from 2000 to 2004 was reviewed. Only patients with clinically negative nodes preoperatively were included. The procedure included preoperative injection of radiotracer, with dye injection as backup, and intraoperative palpation of the axilla for suspicious lymph nodes that were not radioactive or blue. Of the 290 patients, 89 (30.7%) had sentinel node involvement by tumor. Seven patients had clinically suspicious nodes identified solely by palpation and not by tracer, in addition to sentinel lymph nodes detected by tracer. In five of the seven patients, the nodes harbored metastasis. In four of these five patients (4.5% of the 89 patients with axillary involvement), the palpable nodes were the only ones involved. A generous axillary incision and systematic palpation of the axilla reduces the false-negative rate and should be a part of the SLNB procedure.