Inguinal lymph nodes in the Buffalo rat were autotransplanted to the popliteal fossa by an intact vascular pedicle or by microvascular anastomosis. These revascularized nodes had normal histology and made spontaneous afferent and efferent lymphatic reconnection with surrounding lymphatic vessels, as documented by ink and silicone rubber injection studies. Lymphoscintigraphy with 99mTc antimony sulfide colloid correctly predicted the 44 of 120 node transplants that had made afferent reconnection. To demonstrate immunologic activity of lymph nodes following transplantation, a cellular adherance assay was employed to detect cell-mediated cytotoxicity of lymph node cells isolated from rats sensitized to an allogeneic gliosarcoma. Cytotoxicity was detected in nontransplanted regional nodes sensitized to tumor (p less than 0.01) and in nodes transplanted by vascular pedicle and then sensitized to tumor (p less than 0.001). This study demonstrates that lymph nodes can be transplanted with restoration of functional lymphatic anatomy, and that following transplantation, lymph nodes retain the ability to mount an immune response against tumor.