Lymphoscintigraphy was performed in 128 patients with primary lymphedema, in 91 patients with secondary lymphedema, and in 19 healthy volunteers. A total of 457 extremities were examined. Technetium-99m-labeled human serum albumin was injected subcutaneously, and passive muscular exercise was standardized to reduce the variability of lymphatic function. The scintigrams were analyzed for visualization of lymph vessels and lymph nodes, dilatation of lymphatic vessels, existence of collateral vessels, and dermal backflow. With this qualitative interpretation alone, the diagnosis of lymphedema was established in 216 of 308 extremities (70.1%). Quantitative parameters derived from clearance data showed abnormal lymphatic function in all 308 extremities. Whereas qualitative lymphoscintigraphy allows the characterization of lymphatic morphology, quantitative lymphoscintigraphy is very accurate in detection of incipient lymphedema.