Predisposing factors, onset of symptoms to diagnosis interval, computerized tomography findings and the impact of computerized tomography on the outcome were studied retrospectively in 24 patients with renal or perirenal infections. The most common predisposing factors were diabetes mellitus and urinary tract calculi. The mean interval from the onset of symptoms to diagnosis was 6.8 days. The most common computerized tomography findings were thickening of Gerota's fascia, renal enlargement, focal decreased renal attenuation, perirenal fluid and focal gas. Four patients died despite early diagnosis and appropriate therapy. Computerized tomography aided in the diagnosis, assessment of the extent of disease, treatment and followup. Computerized tomography is the most direct method to evaluate patients with suspected renal or perirenal infection, although mortality may not be altered significantly.