Objective Tracking of blood pressure (BP) from childhood occurs in populations but, for individuals, prediction of adult BP from childhood levels is poor. We examined factors that may influence tracking of BP to identify better predictors of higher BP in early adult life.Design A prospective study of children recruited at the age of 9 years by random sampling of Perth metropolitan schools stratified by socio-economic status.Setting Community based with re-surveys 3-yearly for 9 years.Participants A total of 516 boys and 520 girls at 9 years; 680 boys and 630 girls at 12 years; 318 boys and 300 girls at 15 years; 330 men and 326 women at 18 years. Main outcome measures Systolic (SBP) and diastolic (DBP) BP,Results Persistence in the highest quartile for SEP between surveys was seen in 34-48% of subjects and in 37% between the ages of 9 and 18 years. The proportion increased to around 60% in those in the highest quartile for body mass index (BMI), to 70% in those in the highest quartile for change in BMI and to 60% if there was a family history of hypertension, In log-linear models, persistence in a quartile for SEP was significantly related to a family history of hypertension, previous SEP, BMI and change in BMI. Relationships were similar for DBP,Conclusions Excessive weight gain in adolescence and a family history of hypertension substantially increase the risk of higher BP persisting into early adult life. Recognition of children at risk would allow early intervention emphasizing weight control with potential long-term benefits. (C) 2001 Lippincott Williams & Wilkins.