Isosulfan blue dye has been used with increasing frequency in localizing sentinel lymph nodes in breast cancer patients. Few alternative types of dye have been investigated. In a prospective study of 30 patients, methylene blue dye was used instead of isosulfan blue dye to localize the sentinel lymph node. The methylene blue dye localization technique was successful in 90% of patients. These results are similar to those for isosulfan blue dye. This study describes methylene blue dye localization as a successful alternative to isosulfan dye in identifying the sentinel node in breast cancer patients. The methylene blue dye technique offers a substantial cost reduction.