The computed tomographic findings in nine female patients with acute pyelonephritis were reviewed. The major impact of CT was the demonstration of renal enlargement, abnormal contour, perirenal inflammatory extension and, on contrast-enhanced scans, abnormal nephrograms and impaired renal function. It was concluded that CT can provide specific information about the nature and extent of the inflammatory process, thus complementing intravenous urography so that appropriate therapy may be selected. Follow-up studies can be helpful in monitoring the progress of a patient.