Immunolymphoscintigraphy (ILS) refers to lymphatic administration of radiolabeled antibodies for lymph node imaging. Macromolecules such as immunoglobulins are preferentially taken up by lymphatic vessels rather than venous capillaries following interstitial injection. They then travel to regional nodes by lymph flow where they can interact with tumor cells, lymphocytes, or macrophages residing within the node. A variety of radiolabeled antibodies and their fragments have been studied, both in animals and humans, to test their ability to selectively target cells in lymph nodes. Preliminary clinical trials in patients with lymphoma, melanoma, and breast cancer suggest that immunolymphoscintigraphy holds great potential for accurate staging of early malignant disease. The procedure is safe and simple to perform, and offers a noninvasive means to detect small deposits of tumor in regional lymph nodes. Furthermore, direct intralymphatic administration results in even more efficient delivery of immunospecific agents, raising the possibility of radiotherapy by this route.