OBJECTIVE To assess the prevalence of high blood pressure among young children. METHODS This is a cross-sectional study, conducted in 1992 in Colima City, Mexico. Blood pressure readings were obtained from 400 children aged under 19. Statistical analysis consisted of calculation of means, variance, and Anova by group age. Association between age and blood pressure was assessed with correlation and determination coefficients. Comparisons by sex were made using Student's t, F, Mann-Whitney's U, and Z tests. Percentile 95th was used to define normal figures. RESULTS A lineal correlation coefficient was found and confirmed by the determination coefficient. Groups where this association was statistically significant at p < 0.01 were: a) children aged under 2; b) children from 2 to 13 years of age; and c) those over 13 years of age. High blood pressure figures for each group were: a) 92/50 mm/Hg; 110/70 mm/Hg; and 133/84 mm/Hg, respectively. CONCLUSIONS The prevalence of high blood pressure in younger children may be 8% for systolic pressure and 9% for diastolic pressure.