Dynamic imaging of lymphatic flow was performed in 23 patients complaining of lymphedema of the lower extremities. All were injected intradermally with 1 mCi of Tc-99m human serum albumin (HSA) in the medial web on the dorsum of both feet. Image acquisition for the lower pelvis and both thighs was started within 5 minutes. An extra-large field-of-view gamma camera (General Electric 500A) with a low-energy, all-purpose collimator interfaced to a General Electric Star computer was used. Images were acquired in dynamic-byte mode, 128 X 128 matrix size, every one minute up to 40 minutes. Delayed images for the same region and for both legs were taken at 90 minutes. Time-activity curves from equal regions of interest over the inguinal regions on both sides were generated. Three patterns were recognized. Normal flow (12 patients) with symmetric or slightly increased or decreased flow on one side than the other and characterized by early appearance of medial bands, inguinal and pelvic lymph nodes in the early and the delayed images. Time-activity curves showed a stepladder rise in pulses every 3 to 4 minutes. Enhanced pattern (six patients), characterized by fast flow of lymph through the dilated lymphatics, and occasionally by subcutaneous pooling and increase in the number and size of inguinal and pelvic lymph nodes on the affected side.(ABSTRACT TRUNCATED AT 250 WORDS)