A novel method for detecting hypertension in paediatric age groups has recently been formulated using ratios of systolic blood pressure to height (SBPHR) and diastolic blood pressure to height (DBPHR). To validate this approach and assess its applicability to children. A cross-sectional study of 6837 children and adolescents five to 18 years of age was conducted. Blood pressure (BP) readings obtained were stratified using population-based percentiles from the United States. For SBPHR and DBPHR, areas under the ROC curve were >0.9 for BP at or above the 95th percentile. Performance of the cut-off points for detecting elevated BP in adolescents 13 to 18 years of age compared favourably with previous studies, showing high sensitivity and specificity (>95%). SBPHR and DBPHR also proved satisfactory when applied to children five to 12 years of age. Nevertheless, performance was lower for BP between the 90th and 95th percentiles. BP to height ratios are a practical means for detecting elevated BP in adolescents and children.