Purpose: Lymphoscintigraphy and sentinel node biopsy has become a standard method for detection of axillary lymph node metastasis in breast cancer patients, but the standard radiopharmaceutical was not prepared. About detection of axillary lymph node metastasis by lymphoscintigraphy and sentinel node biopsy in breast cancer patient, we compared the results of Tc-99m Tin-colloid and Tc-99m Phytate by subareolar injection. Materials and Methods: This study included 382 breast cancer patients who were performed operation during 2001-2008. Three hundred forty nine patients was injected 0.8 ml of Tc-99m Tin-colloid (37-185 MBq) by subareolar injection. Thirty three patients was injected 0.8 ml of Tc-99m Phytate (37-185 MBq). Lymphoscintigraphy was performed in supine position and sentinel node localization was performed by hand-held gamma probe in operation. Result: Among 349 patients by Tc-99m Tin-colloid, 312 cases (89.4%) localized the sentinel node by lymphoscintigraphy, 304 cases (87.1%) localized by gamma probe. Among 33 patients by Tc-99m Phytate, 32 cases (97.0%) localized by lymphoscintigraphy, 33 cases (100%) localized by gamma probe. Detection rate by lymphoscintigraphy and gamma probe was superior for Tc-99m Phytate compared to that with Tc-99m Tin-colloid, with a statistically significant difference. (p<0.05, p<0.05) Conclusion: Tc-99m Phytate is a better choice for localization of sentinel node than Tc-99m Tin-colloid in breast cancer patients. (Nucl Med Mol Imaging 2008;42(6):451-455)