Forty cases were examined by a new lymphoscintigraphic approach using intradermal injections of Tc-99m human serum albumin (HSA). Thirty-three patients had lymphedema due to the metastases of a malignant tumor and/or the dissection of lymph nodes. The others were control patients without lymphedema. With the assistance of a computer, sequential images and time-activity curves of tracer activity in the lymph nodes and the soft tissue were obtained at 30 minutes after injection. An image of the axillary or inguinal lymph nodes was identified 2-6 minutes after injection in control cases. Four main abnormal findings, the delayed appearance of radioactivity and interruption of the lymphatic system, the collateral pathways, and the retrograde lymphatic flow were observed clearly, as was the nonvisualization of the lymph nodes. These abnormalities were observed in a high percentage of patients with moderate lymphedema, as compared with a low percentage of patients with slight lymphedema. The collateral pathways could not be observed in patients with severe lymphedema. Imaging with Tc-99m HSA was considered to be more useful than other techniques, including radiocolloid lymphoscintigraphy, for examining patients with lymphedema.