Abstract: The techniques for performing sentinel lymph node biopsy (SLNB) vary from institution to institution. Some advocate blue dye only, others radioisotope only, and many utilize a combination of both. The purpose of this study is to evaluate the additional benefit that blue dye provides when used in combination with a radioisotope. From October 2001 to June 2004, 102 SLNBs were attempted in 99 patients with breast cancer using a combination of blue dye and radioisotope. A lymph node was considered a sentinel lymph node (SLN) when it was stained with blue dye, had a blue lymphatic afferent, or had increased radioactivity. Ninety-eight patients had 101 successful identifications of SLNs, for an identification rate of 99%. Twenty-eight patients had positive SLNs. In three of those patients, although there were SLNs identified by both techniques, the positive SLNs were identified with only blue dye. Of the 102 SLNB procedures, there were two patients whose only SLN was identified by blue dye only. Although blue dye did not improve the identification rate, there was a definite benefit in improving the false-negative rate.