Purpose: The purpose of this study is to determine characteristic CT findings in renal abscess. Material and Methods: Twenty cases of renal abscess were retrospectively analyzed for CT findings relating to the shape and extent of the abscess, change of nephrogram, peripheral rim enhancment, wedge-shaped enhancement on delayed scans,enlargement of the kidney involved and associated findings. Results: Seven patients had a renal abscess at the right kidney, nine at the left kidney and two bilaterally. The abscesses were round in 18 cases and finger-like in two. Rim enhancement around renal abscess was seen in four cases(20%). Changes in the nephrogram around the abscess were seen in 12 cases(60%). In all six patients who had undergone delayed postcontrast scans, wedge-shapedenhancement was shown around the abscess(100%). In the observation of the extent of renal abscesses, 14 cases were within the kidney, six cases extended the beyond renal capsule, and two were loculated in the renal fascia itself.Renal enlargement was seen in nine cases(45%). Conclusion: These results suggest that CT findings such as delayed wedge-shaped enhancement, change of nephrogram, peripheral rim enhancement, renal enlargement, and associated findings are valuable for diagnosis, and that CT also gives information concerning the extent, evolution and complication of a renal abscess.