Sentinel lymph node biopsy for breast cancer is reviewed herein. It has been recently investigated at many hospitals and institutes, mainly in Europe and the USA. Two lymphatic mapping methods using radiolabeled colloids and dyes are the most popular for detecting the target nodes, and seem to become a standard method of sentinel biopsy. A learning curve for identifying sentinel lymph nodes is important in improving the accuracy of detection. However, it should also be noted that a certain number of false negative cases are usually found. Furthermore, a highly reliable and suitable method to examine lymphatic metastasis has not yet been established. Large clinical trials need to be performed to confirm the optimum method for this new treatment for breast cancer.