Rat and dog kidneys were injected withsilicone rubber (Microfill<sup>R</sup>) and the surrounding tissue cleared with methylsalicylate. Casts of several hundreds of vascular poles of glomeruli were studied under a stereomicroscope. No shunts between afferent and efferent arterioles could be demonstrated either in the outer cortical or in juxtamedullary glomeruli. For documentation purposes scanning electron micrographs were taken. Vasa recta vera were only found in old rats.