The studies of blood pressure (BP) in the adolescence are important because the growth and development, as well as the exposure to risk factors that begins in this period gives a good opportunity to make research on the behavior of BP and its modification in adulthood. We carried out a transversal study. Our sample was made by random conglomerates, multistage; we studied 1,123 children from 12 to 15 years on Mexico City. The behavior of the BP cifers for the males was that as age increases they increase at an average of 3 mmHg per year, in females we did not find this. When we compared the percentilar values by age and sex with studies carried out in the US, we had similar results.