Renal bacterial infection spans a continuum of severity from uncomplicated acute pyelonephritis through progressively worsening stages of interstitial inflammation to abscess formation. This study was done to evaluate CT findings in acute bacterial renal infection and correlation of clinical symptoms and renal scarring with CT findings. We studied 58 cases of acute pyelonephritis who were diagnosed clinically. Most of them had prolonged fever( >72 hours) and some of them suspected severe renal infections. We classified the patients regarding to CT findings. 58 cases were grouped into, 1) Group I (7 cases), normal or renal enlargement only; 2) Group II(31 cases), wedge-shaped lesions ( focal or diffuse) , 3) Group III(6 cases), focal mass-like lesions; 4) Group W(9 cases) , diffuse ( multifocal) mass-like lesions; 5) Group V (5 cases) , renal abscesses. There was the good correlation between the clinical parameters ( duration of fever, duration of hospitalization) and CT findings (P < 0.05). However, another clinical parameters(maximum temperature, duration of fever) were lacked correlation with CT findings(P >0.05). To demonstrate the presence of renal scar, we recommended DMSA scan in 15 cases of ABN (Group III and Group IV). 8 cases were performed DMSA scan and renal scar formation was found in 3 cases( 2 cases in Group III and another 1 case in Group IV). Because the size of abscess was small( <3cm), the patients of renal abscess(5 cases) were treated with antibiotics only and their clinical symptoms were improved. Second CT scanning was performed in 3 cases and their CT findings showed resolution of renal abscess. We concluded that computed tomography is selectively indicated in acute renal bacterial infection for the detection of acute renal inflammatory disease and for defining the extent of disease for planning of treatment.