As part of an epidemiological study on cardiovascular risk factors among children and adolescent in Navarra, arterial blood pressure (BP) readings were taken in 5,829 children. These children, both males and females, between the ages of 4 and 17 years, were selected at random from the public and private school population in our community. The correlation between systolic blood pressure and diastolic blood pressure with anthropometric and biochemical parameters was analyzed. The correlation coefficient for systolic BP readings were always higher than those for diastolic BP. The highest correlations for both BP scores were found with weight, followed by height. Correlation with total weight parameters is superior to that found with body fat parameters. There were no significant correlations between BP and the lipid parameters. When analyzing multiple regression equations, we find that with only the child's weight and age, both systolic and diastolic BP can be predicted with correlation coefficients of 0.597 and 0.492, respectively. When doing a partial correlation analysis, the correlation between systolic BP and age, at a fixed height value, disappears; while the correlation of systolic BP with height remains when using a set age. This suggest that the best definition for hypertension is based on BP-height percentile, rather than BP-age.