Intravenous urography, systematically performed in 50 consecutive acute pyelonephritis patients, revealed abnormalities in 17 of them: in 12 cases (24%), treatment and follow-up were modified; in the other 5 cases (10%), the anomalies were insignificant. The nephrogram was normal for 33 patients (66%). The frequency of significant abnormalities was higher in patients over 50 years of age (46.2%) than in those under 50 (16.2%) (p less than 0.05), and was also higher in patients remaining febrile for 3 days after the onset of an appropriate antibiotic therapy (66.6%) than in responsive patients (14.4%) (p less than 0.01). Among the significant lesions, 10 were detectable by echography and another by abdominal X-ray. Thus, a population of women under 50 years of age with acute pyelonephritis can be selected for urography, as shown by these results, however, they must be confirmed before changing the systematic practice of urography.