The initial draining lymph node (Sentinel node) of a tumour may reflect the status of the tumours spread to the remaining lymphatic bed. The sentinel node, which has been reported to predict metastatic melanoma, has recently been localized by a new invasive technique [1]. The goal of our pre-clinical trial was to test a non-invasive technique to localize the sentinel node. Gamma-probe guided localization was used to identify and then surgically remove the first draining lymph node(s) in 16 inguinal lymphatic basins of eight cats. This method was found to be comparable to an invasive method using a blue dye. Gamma-probe localization has several potential advantages in that it can: (a) precisely locate on the surface of the skin the position of an underlying lymph node, (b) intraoperatively guide the surgeon to the lymph node during dissection, (c) verify that the correct node has been biopsied, (d) determine the possible presence of residual lymph nodes, (e) allow lymph nodes to be harvested through a small incision as opposed to raising a skin flap, and (f) be rapidly and easily performed.