It is now generally known that the renal glomerular podocyte slits are made of ‘nephrin’ which was identified as a molecule responsible for the urine filtration barrier. However, by careful observation of all immuno-electron microscopic findings on its localization so far published by various authors, it should be noted that no convincing evidence is present for the localization of nephrin-immunoreactivity in the slit itself. Instead, their immuno-electron micrographs rather suggest that nephrin- immunoreactivity is dominantly localized along the membranes of podocyte pedicles from their tip over a substantial extension. In addition, it should also be noticed that the thickness of ~0.5 mm of the intensely immunopositive bands for nephrin in immuno-light microscopy is incompatible with that of the slit structure less than 5 nm thick, which is below the light microscopic resolution. Even when the slit structures of such a thinness are supposed to be contained obliquely in thick light microscopic sections and they would be immunostained and viewed in rather en-face directions, the appearance of such thin and immunostained targets must not be intensely stained lines in light microscopy, but be vague sheets.  It is therefore suggested that the localization of nephrin in the slits is not confirmative, and it should be re-examined.