Cases 1 and 2 were a 84-year-old, 64-year-old female relatively. Case 2 had a history of uncontrolled diabetes mellitus. Both cases were referred to our hospital with a chief complaint of high fever. Initial diagnosis was acute pyelonephritis based on the findings of pyuria and right costovertebral angle knock pain. Abdominal computed tomography (CT) scan revealed a gas shadow in the right renal pelvis and calyx with right ureteral stone. The definitive diagnosis was emphysematous pyelonephritis (EPN). We selected transureteral catheterization into the right ureter immediately. Escherichia coli was identified from urine culture. Conservative therapy with antibiotics was also effective and general condition improved. Herein we discussed the etiology, symptomatology, choice of treatment and prognosis of emphysematous pyelonephritis. Recently CT is an effective imaging method for diagnosis at an early stage. Antibiotics therapy combined with transureteral drainage of gas-forming urolithiasis is effective as the initial conservative therapy.