The purpose of this study was to determine the prevalence of persistent blood pressure elevation in school children. Mass screening of blood pressure was performed simultaneously with a cardiovascular health check in school children. Forty four hundred and eighty school children were selected as subjects for this study, consisting of 2289 first grade primary school students aged six and seven (group A), and 2191 second grade junior high school students aged thirteen and fourteen (group B). Of the 4480 students, 4031 were examined at the initial blood pressure screening. Three hundred and sixty students whose systolic and/or diastolic pressures were above the 95th percentile were recalled for a second examination. Three hundred and thirty one students were studied at the 2nd examination, and 69 students were listed for a third survey. 1.7% of the original subjects were examined at the final survey. At the first screening, mean blood pressures were 101.5 +/- 8.5/61.2 +/- 6.6 mmHg (mean +/- SD) for males and 100.3 +/- 8.3/60.9 +/- 6.5 for females in group A. In group B, blood pressures were 120.2 +/- 11.3/66.6 +/- 7.4 mmHg for males and 117.4 +/- 11.2/66.9 +/- 7.8 mmHg for females. This screening system, if incorporated into the school health program, is an effective and efficient method of screening for persistent blood pressure elevation in school children in Japan.