A 56-year-old female presented with end-stage renal disease. A CT scan of her kidneys demonstrated that the density of the renal parenchyma was quite low as compared with normal kidneys, and that corticomedullary demarcation was obscured. Magnetic resonance imaging (MRI) disclosed low intensity of the kidneys in T1-weighed images, and high intensity in T2-weighed images. In order to elucidate the etiology of her kidney disease, open renal biopsy was performed. The kidney surface was covered with numerous cysts with a diameter of less than 3 mm. Biopsy specimens from the cortical surface showed multiple cystic lesions. Serial sections of more than 200 slices of the biopsy material demonstrated that traces of collapsed glomeruli were present in most of the cysts. On electron microscopy, some epithelial cells lining the cysts were found to be round-shaped and contained a substantial amount of mitochondria, suggesting proximal tubules. These histological findings were compatible with glomerulocystic kidney disease (GCKD). An adult case of GCKD has rarely been reported, but the CT scan as well as MRI of the kidneys appeared to complement the diagnosis of GCKD. Although the cysts of GCKD have been considered to be dilatations of the Bowman's capsules, our observation suggested that part of the cells lining the cysts consisted of proximal tubular epithelium.