Sentinel node biopsy is a promising surgical technique to avoid unnecessary axillary lymph node dissection for breast cancer patients with histologically negative nodes. Several randomized phase III trials in Western countries are underway to assess sentinel node biopsy in cases of breast cancer in comparison with conventional axillary lymph node dissection. Other investigators have also started observational studies in cases when sentinel lymph nodes are proven histologically negative. In Japan, many issues regarding this minimally invasive surgery remain unresolved: optimal procedure, pathologic work-up, radiation exposure, health insurance coverage, and indication for sentinel node biopsy. The current status and problems of sentinel node biopsy in breast cancer are discussed herein.