The clinical and laboratory features of urinary tract infection were studied on symptomatic as well as asymptomatic children. Among 77950;, 68(0.09%) had significant bacteriuria in asymptomatic schoolchildren in Chiba City in 1977. E. coli was found to be the main cause. Radiological examination was performed in 13 of the 68 children. Vesicoureteric refluxes and neurogenic bladder dysfunction were found in 8(61.5%) children. Follow-up study six month later revealed that 56 children were under medical care and 47(84%) were free from infection. On the other hand, symptomatic urinary tract infections were studied on outpatient children visiting the Department of Urology, Chiba University, during the period of 1975 to 1977. Among total 1327 outpatient children, 215(16.2%) revealed to have urinary tract infections (cystitis: 82, vesicoureteric reflux: 24, pyelonephritis: 22, vulvitis: 19, neurogenic bladder dysfunction: 14, urolithiasis: 14, etc). Various organisms such as E. coli: 21, Krebsiella: 5, Enterobacter: 3, Proteus: 2, Staphylococcus: 2 were isolated from these patients.