The objective of the study was to determine the prevalence of hypertension in healthy primary school children. A cross-sectional survey by manual blood pressure measurement of healthy children aged 6-12 years attending a national type school was carried out. Children with previous renal, cardiac and endocrine disorders were excluded. Korotkoff 1 represented the systolic blood pressure (SBP) and Korotkoff 5 was taken as the diastolic blood pressure (DBP). Hypertension was defined as the SBP or DBP above the 95th centile according to age group and sex regardless of ethnicity. A total of 1756 children were studied with 895 boy and 861 girls. The results showed that 109 children (6.2%) were found to have hypertension and the incidence was similar in boys and girls (6.4% vs 6.0%, p = 0.69). Fifty-three (48.6%) children had an elevated SBP and the DBP was elevated in 43 (39.4%) children. Only 12 (12.0%) children had both elevated SBP and DBP. Children found to have hypertension were more likely to be Chinese (p = 0.009) and obese (p = 0.04). In conclusion the overall prevalence of hypertension in children aged 6-12 years based on a single blood pressure measurement was 6.2%. Hypertension was more likely to be found in Chinese children and those who were obese.