Urinary tract infection, one of the commonest bacterial diseases in children, carries a substantial risk of serious complications. Amongst them, renal scarring and recurrent infections seem to be the most important. In this review, we analyze the pathogenesis of urinary tract infection in order to identify those children who run the highest risk of unfavorable outcome. During infection, multiple bacterial and host factors interact with each other. Bacteria possess specific characteristics involved in the process of adhesion, invasion, survival and host damage during infection. Host factors also substantially participate in the pathogenesis of the disease. According to current knowledge, the specific host response appears to be the main factor predisposing for complications. However, prompt and adequate treatment of acute urinary tract infection remains the most important measure to prevent scarring. Dysfunctional holding and elimination of urine, on the other hand, mainly seem to influence the development of recurrent infection. Despite intensive research for many years, urinary tract infections are still a challenge for patients and health care professionals.