Chronic lower-leg edema in patients with venous disorders was studied by means of lymphoscintigraphy. Lymphatic patterns of flow were evaluated prospectively in 26 patients with technetium 99m antimony trisulfide colloid injected subcutaneously in the interdigital web spaces on the feet. Most patients in this study had postphlebitic syndrome, and all of these patients had abnormal lymphoscintigraphic flow patterns. Nine had evidence of lymphatic obstruction, and one had an enhanced flow pattern. Three patients had veins used for distal arterial bypass, and all these veins showed decreased lymphatic flow. Two patients with Klippel-Trenaunay syndrome (congenital varicose veins associated with limb elongation, a capillary nevus, and an abnormal deep venous system) had obstruction to lymphatic flow, and two others had normal and enhanced patterns. Normal studies were seen in four of five patients who had veins used for coronary artery bypass grafting. The finding of decreased lymphatic flow in patients appears to be the result of the length of time from an episode of deep venous thrombosis, the occurrence and number of episodes of cellulitis and lymphangitis, and mobilization of the vein for use in distal arterial bypass surgery. This study shows that the edema attributed previously to primary venous disorders may have a significant lymphatic component. The degree of lymphatic obstruction can be determined by lymphoscintigraphy with technetium-labeled antimony trisulfide colloid.