The tissue clearance of iodide was studied in relation to capillary flow as estimated by xenon clearance in dog skeletal muscle at prolonged graded arterial occlusion. While transport of iodide was diffusion-limited at control in resting muscle, there was, shortly after reduction of flow and perfusion pressure, a transient state of flow-limited transport, which changed within 1 h towards diffusion-limited transport, now reduced, compared to control at comparable flows. This state of disturbed transport could be reversed by release of occlusion or by low molecular weight dextran infusion at unchanged low perfusion pressure. This pattern of changes of iodide transport in relation to flow and to perfusion pressure at prolonged low perfusion pressures was identical with that seen during the progress of hemorrhagic shock. The changes of iodide transport were interpreted as due to an efficient transport by opening of capillaries and a lower linear rate of flow at reduced flows, changing, however, at prolonged occlusion, towards an uneven flow distribution, with a subsequent reduction of the efficiency of transport of iodide.