The microvascular pattern of the feline renal medulla was studied by scanning electron microscopy using corrosion casts. At the corticömeduUary junction, numerous efferent arterioles were observed giving rise to peritubular capillary plexuses and arteriole rectae. Considerable differences in vessel diameters were seen. Arteriolae rectae coursed around interlobar veins before returning to the corticömeduUary area, as venulae rectae. Diffuse capillary papillary plexuses were seen protruding into the renal pelvi