High resolution separation of metalloproteins and other iron compounds based on native gel electrophoresis followed by 59Fe autoradiography is described. Lysates of mouse spleen erythroid cells metabolically labeled with 59Fe-transferrin were separated on 3-20% polyacrylamide gradient gels in the presence of Triton X100 and detected by autoradiography. In addition to ferritin and hemoglobin, several compounds characterized by their binding of iron under different conditions were described. Iron chelatable by desferrioxamine migrated in the region where several high-molecular weight compounds were detected by silver staining. The technique is nondissociative, allowing identification of iron compounds with the use of specific antibodies. Cellular iron transport and the action of iron chelators on specific cellular targets can be investigated in many small biological samples in parallel.