Abstract: Urinary Tract Infection (UTI) is a relatively common infection in children that can lead to serious complications such as renal scarring, hypertension and chronic renal failure. In this study we stressed the role of IL-8 in the diagnosis and differentiation between pyelonephritis and cystitis. This prospective descriptive study was conducted among 86 children one month to 14 years, who with clinical signs and symptoms of suspected urinary tract infections were referred to Ahvaz Aboozar hospital. Among 86 children studied 16 (18.6%) and 70 (81.4%) children were boy and girl, respectively. E. coli and Klebsiella were obtained from urine samples of 72 patients (83.7%) and seven patients (8.1%), respectively. The frequency of abdominal pain in pyelonephritis and cystitis groups was 10.4 and 18.4%, respectively. Vomiting in the pyelonephritis and cystitis groups was respectively 22.9 and 10.5%. The frequency of diarrhea in the pyelonephritis and cystitis groups was 4.2 and 2.6%, respectively. In general, dysuria was the most common symptom in the two groups (69.8%). Measurement of cytokines only takes a few hours and to do it is the easy and non-invasive. Based on the study system the mean IL-8/Cr for detecting pyelonephritis in level 7 has the sensitivity of 66% and the specificity of 72% and even the increased IL-8 after the initial experimental treatment can be a sign for the continued inflammation or antibiotic resistance. Obviously, in this recent case wider study must be carried out.