Acute idiopathic tubulointerstitial nephritis (TIN) is considered a condition with a good long-term prognosis. However, there is evidence that some patients develop permanent renal impairment. The aim of this study was to evaluate the clinical characteristics of TIN at the time of diagnosis in children and determine whether the findings upon presentation predict renal outcome. The clinical data and biopsy findings from 26 children with idiopathic TIN admitted to four Finnish university hospitals were analyzed retrospectively. Twenty-five patients (96%) manifested renal insufficiency. After the mean follow-up time of 2.75 years (SD 2.5; 0.9-13.5), 4 patients (15%) had permanent renal insufficiency and 8 patients (31%) had persistent low-molecular weight proteinuria. Uveitis was found in 12 patients (46%). Four of these patients (33%) developed chronic uveitis. Our analysis showed that none of the laboratory or biopsy findings upon presentation prognosticated renal outcome. No correlation between renal disease and uveitis could be found either. The occurrence of uveitis among TIN patients was higher than previously reported. Uveitis may develop late and without recurrence of renal dysfunction. Therefore, follow-up by a pediatrician and by an ophthalmologist is warranted in children with acute TIN for at least 12 months from diagnosis.