The author is conducting systematic screening surveys for bacteriuria among the pupils in the primary schools (6-14 years) of a provincial town and environments. He applies the nitrite reaction for the detection of bacteriuria. Over the past 5 years 16,621 children, 7982 girls and 8639 boys, were screened, part of them repeatedly. Four bacteriuric cases were diagnosed among the boys and 130 among the girls. In a single screening the prevalence rate of bacteriuria proved to be 1.23% among the girls. In repeated screenings the incidence rate was 0.44% on the average per annum. Fifty-six of the 130 bacteriuric girls were subjected to general examination; radiological abnormalities were found in 26 of them. The author considers the systematic screening of schoolchildren as reasonable. The nitrite reaction is the most appropriate for mass screening, since it is simple, immediate, inexpensive, specific and sufficiently sensitive.