Childhood UTI is a common bacterial infection in children and frequently associated with urinary tract anomaly and high recurrent rate. Recurrent UTI and even the first UTI, if not diagnosed and untreated, may lead to serious renal scarring, a cause of childhood hypertention and end stage renal failure. It is very important to prevent the sequence of recurrent UTI and the development of renal scarring from the first UTI. However, early diagnosis is very difficult because the symptoms and signs are non-specific in young children and commonly presented with high fever only. In young infants with unexplained high fever, urinalysis and urine culture should be considered for early diagnosis. Emperic antibiotic treatment should be initiated in suspicious UTI and imaging studies of the urinary tract should be performed for the evaluation of urinary tract anomaly and renal scar in confirmed cases of UTI. Antimicrobial prophylaxis has been the common clinical practice in children with high risk factors for recurrent UTI and renal scar. In summary, early diagnosis and proper management of childhood UTI are very important to prevent hypertention and end stage renal disease by renal scar.