An avascular glomerulus, measuring about 30μ in diameter, composed only of atrophic epithelial and undifferentiated mesenchymal cells was found in the kidney of a normal male rat. There were no afferent and efferent arterioles associated with this glomerulus, but a blood capillary with some juxtaglomerular cells occurred at its pole. This glomerulus was considered to be derived from a malformation in nephrogenesis and to be in the process of becoming hyalinized. Discussion was made with reference to the pathogenesis of so-called congenital glomerulosclerosis.