PURPOSE: The purpose of this study was to evaluate the CT findings of acute pyelonephritis (APN) in children and to assess the correlation between these findings, clinical parameters and renal scar development, as seen on follow-up CT scans. MATERIALS AND METHODS: Contrast-enhanced CT scans of thirty children in whom APN had been diagnosed were assigned to one of three groups according to whether an abscess had formed, and then to subgroups on the basis of the number of lesions in the renal parenchyme. Initial CT findings were retrospectively correlated with five clinical parameters (maximal body temperature, fever duration, leukocytosis, pyuria and admission period) and renal scar development, as seen on follow-up CT (n=12). RESULTS: CT scans demonstrated linear, wedge-shaped, low-density renal parenchymal lesions in 35 kidneys of 25 patients and abscesses in seven kidneys of seven patients, but no abnormal lesions in five patients. In the three groups there was correlation between these findings and some clinical parameters (maximal body temperature, fever duration and admission period), but no subgroup showed significant correlation with any clini-cal parameter. Renal cortical scars detected by follow-up CT were more prevalent in patients in whom initial CT demonstrated the presence of an abscess. CONCLUSION: Clinical parameters correlated with the presence of renal parenchymal hypoenhancing lesions and abscess formation, as seen on CT scans, rather than the number of renal parenchymal lesions. Renal cortical scars were more prevalent in patients in whom initial CT revealed the presence of an abscess. Enhanced CT is thought to be useful both for diagnosing APN and for predicting its clinical course in children.