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Introduction: Rapid and sensitive diagnostic tests for urinary tract infection (UTI) are currently lacking and suspected episodes require urine culture . The present study compared the predictive values of urinary dipstick and automated flow cytometerurinalyses as diagnostic tests for UTI in febrile children Material and methods: We prospectively collected data on 1247 febrile episodes in 1224 children. Urine was assessed for white blood cell (WBC), red blood cell (RBC) and bacterial counts using an automated flow cytometer. Urinary leucocyte esterase and nitrites were tested by dipstick and the diagnosis of UTI established by urine culture. The diagnostic performance of these tests and their optimal cut-off points to diagnose UTI were established using receiver-operating characteristic (ROC) analysis. Reduction of diagnostic uncertainty by cytometer analysis was modeled for populations with different prevalences of UTI. Results: Urinary and biological data were analyzed for 1247 infectious episodes, among which 221 UTI (17.7%). The area under the ROC curve for cytometer WBC counts (0.99) was significantly superior (P < 0.0001) to urinary dipstick analysis (0.92), RBC (0.74) and bacterial counts (0.89). For cytometer WBC counts, the presence of ≥35 WBC/μl was the most useful cut-off point, yielding both high sensitivity (99.5%) and acceptable specificity (80.6%). Only one episode of UTI was associated with a WBC cytometer count of