Lymphoscintigraphy along with a gamma-detecting probe has been applied successfully to breast cancer patients to localize the sentinel node during surgery, with a 5% false-negative rate. The authors report a case of stage II breast cancer. The sentinel node was not visualized on the initial lymphoscintigraphy with peritumoral injection of 37 MBq (1 mCi) 10 ml Tc-99m colloidal rhenium sulfide (Tc-99m ReS colloid; average particle size, 100 nm). However, the sentinel node was visualized in the left lateral view of the second lymphoscintigraphy with peritumoral injection of 37 MBq (1 mCi) 10 ml Tc-99m ReS colloid (average particle size, 500 nm). Lymphoscintigraphy using the larger colloid particles may enhance visualization of a sentinel node in breast cancer.