IVP is simple, noninvasive screening examination of the kidneys and is helpful for evaluation of the functional and structural changes if the pyelogram was obtained. Unilateral nonvisualizing kidney may be resulted from various diseases that can produce vascular obstruction, functional deterioration of the glomerular filtration and obstruction of the lower urinary tract. In cases of nonvisualizing kidney further study including RGP, renal angiography, CT, ultrasonography and RI imaging is needed. During the period of 10 years from 1972 to 1981, 100 cases of nonvisualizing kidney which could be diagnosed by other imaging studies. The authors reviews medical records and findings of RGP, renal angiography, CT and ultrasonography of the nonvisualizing kidneys. The results were as follows : 1. The material included 53 male and 47 female patients. The age distrubution was broad, but mostly in the twenties and fourties of ages. 2. There was no remarkable differences between sides of involvement in both sexes. 3. The underlying diseases of nonvisualizing kidney on IVP were renal tuberculosis (33 patients), ureteral stricture (16 patients), ureteral stone (12 patients), renal tumor (10 patients), pelvic mass (10 patients), chronic pyelonephritis (8 patients), renal agenesis (5 patients), renal trauma (4 patients), and renal disease of vascular origin (2 patients) respectively. 4. RGP was performed in 79 out of 100 cases. RGP was the most confirmative diagnostic procedure in cases of inflammatory diseases of the kidney and renal plevic tumors. 5. Renal angiography was performed in 19 cases. Renal angiography was very helpful in the diagnosis and evaluation of the extent of the diseases in 6 cases of renal tumors, 3 cases renal trauma, 2 cases of renal vascular diseases and 3 cases of renal agenesis. 6. Body CT was performed in one case of renal cell carcinoma and other 6 cases of hydronephrosis mainly from tumors of the pelvic cavity including 4 cervical carcinomas and a bladder carcinoma. CT was very useful for evaluation of extent of the diseases and regional or intraabdominal distant metastasis in one examination. 7. Ultrasonography was performed in 18 cases of various diseases. The size and gross contour of the kidney, hydronephrosis and focal masses were easily detectable with ultrasonography. In these cases, the confirmative diagnosis could be made by other studies including RGP or Renal Angiographies.