The aim of this study was to determine the association between blood pressure and the frequency of structured physical training activity in Chinese adolescents. A total of 9558 students aged 11-18 years underwent anthropometric and blood pressure measurements in a cross-sectional growth study. Structured physical training activity was assessed by two simple self-administered questions and parents were asked to complete a questionnaire providing demographic information. Ninety per cent of eligible students participated in the study, of which 94% provided data on physical training frequency for final analysis. Of the boys, 22.6% and of the girls, 14.5% were physically active with extracurricular school exercise at least twice a week. Over half of the students did not regularly exercise except during physical education classes at school. Blood pressure had a positive correlation with body mass index (BMI). Both systolic blood pressure and diastolic blood pressure were substantially decreased with increased training frequency (P<0.05). Logistic regression adjusting for age, family history of hypertension, BMI and sleep duration showed that exercising two or more times a week had a negative relation with hypertension (odds ratio: 0.63, 95%CI 0.47-0.85). In conclusion, structured physical training activity of two or more times a week has a beneficial effect on blood pressure in Hong Kong children aged 11-18 years.