At present, 99Tcm-dimercaptosuccinic acid (DMSA) renal scintigraphy is the most sensitive examination for the detection of parenchymal damage during acute pyelonephritis (APN) in children. This prospective study had three aims: (1) to evaluate the medium-term evolution of the scintigraphic abnormalities, to find a prognostic criterion of scintigraphic evolution; (2) to assess the correlation between the severity of early or late scintigraphic damage and selected clinical factors; and (3) to compare the permanent scintigraphic renal scars with intravenous urography (IVU) 2 years after the acute infection. Seventy-four children (mean age 32 months), presenting with a first clinical episode of pyelonephritis and an initial scintigraphic abnormality, were included in the study. Patients with a history of urinary tract infection (UTI), uropathy other than vesico-ureteral reflux (VUR) and a relapse of acute pyelonephritis were excluded. All children underwent control scintigraphy (mean 9 months after APN) and 43 had an IVU (mean 26 months after APN). Fifty-seven children (77%) still have scintigraphic abnormalities of varying severity (7 atrophic kidneys). Initial relative DMSA uptake of less than 45% results in a worse scintigraphic prognosis. The age of the child has no bearing on the severity of the initial renal involvement or on the evolution of the scintigraphic abnormalities. The rapid introduction of antibiotics (< 12 h) significantly improves the scintigraphic prognosis (P < 0.01). The presence of reflux (n = 39) leads to more serious initial damage, but we did not find any effect on later evolution in this study, in which all reflux was low grade in nature. Among the 43 children who had an IVU, 5 showed typical urographic and scintigraphic renal scars in the corresponding region and 38 showed a normal IVU with 28 cases of scintigraphic abnormalities. A DMSA scan is more sensitive than IVU for the detection of renal scarring after a first episode of APN.