There are complications in diagnosing hypertension in children and adolescents due to variation of blood pressure (BP) values to age, gender and height. This study was aimed at assessing whether the performance of BP-to-height ratio (BPHR) can be an effective tool for screening prehypertension and hypertension in Ellisras Longitudinal Study (ELS) children aged between 6 and 17 years. A number of the 9002 children aged 6-17 years who were part of the ELS underwent height and BP measurements using standard procedures. Receiver-operating characteristic curve was used to assess the accuracy of BPHR to screen children with prehypertension and hypertension. The optimal systolic BPHR (SBPHR) and diastolic BPHR (DBPHR) cut-off points for hypertension were determined. Sensitivity/specificity, positive predictive values and negative predictive values were calculated. The optimal thresholds for defining prehypertension was 0.77 in children aged 6-10 years and 0.73 in adolescents aged between 11 and 17 years for systolic BPHR and 0.55 in children and 0.53 in adolescents for diastolic BPHR, respectively. The corresponding values for hypertension stage 1 were 0.76 and 0.73 for SBPHR and 0.50 and 0.58 for DBPHR, respectively. BPHR can be used as an effective tool for screening both prehypertension and hypertension in ELS children aged 6-17 years.