A case of juxtaglomerular cell tumor, the fourth case in the world diagnosed preoperatively, was reported. Neither strict sodium restriction nor loading of upright position increased a grade of hyperreninemia observed at recumbent position on ordinary diet, but Paid elevated in response to them. Abnormal glucose tolerance was considered to be due to hypopotassemia. Selective renal arteriography revealed a small number of tumor vessels, a lucent area on the nephrogram and early appearance of the renal vein of the diseased side. Histologically, the tumor contained some canalicular structures among the polygonal nonepithelial tumor cells with rhomboid bodies. These findings suggested that this tumor was a hamartoma originated from the juxtaglomerular apparatus.