Tc-99m autologous-labeled leukocyte scintigraphy is widely used to detect sites of abscess and infection. The authors report two cases in which persistent tracer uptake was found in patent, non-infected, asymptomatic vessels. One was in a lower extremity varicosity in a patient being screened for inflammatory disease of the opposite ankle. The other was in a prosthetic aorta-to-right common femoral artery by-pass graft, that was found to be noninfected by intraoperative swab biopsy. Persistent uptake in patent, noninfected vessels has not previously been reported. The cause of this persistent margination of radiolabeled white blood cells is unknown. These cases suggest the need to consider a noninfectious etiology for white cell localization in varicosities and by-pass grafts.