Dextran sulphate is often used as a model for albumin in understanding capillary-tissue exchange and the charge selective nature of the capillary wall, particularly in kidney ultrafiltration. In investigating the mechanism of transport in the kidney, autoradiographic analysis of the distribution of iodinated dextran sulphate in perfused rat kidneys demonstrates the preferential accumulation of the probe in the glomerular capillary wall. Tritium-labeled dextran sulphate is found to be specifically taken up by intracellular 20 to 40 nm vesicles that can be isolated post-perfusion. The molecular weight profile of vesicular dextran sulphate demonstrates that the dextran sulphate containing vesicles are from vascular glomerular cells. Dextran is not taken up by the vesicles. These results suggest that the apparent charge selectivity associated with the transglomerular transport of the dextran sulphate is associated, in part, with cell-mediated processes at the glomerular level.