OBJECTIVE: To study the relationship between obesity and the serial blood pressure measurements in children. METHODS: Two hundred and thirty-five Grade One pupils from Hefei City were included in the study and vital signs (blood pressure, height, weight, heart rate, etc. ) were measured once a year. A 4-year follow- up for them was performed to study the changes of blood pressure. RESULTS: Blood pressure gradually increased over time. A significantly positive correlation was found between the initial blood pressure and successive blood pressure values obtained during the follow-up. Correlation coefficients of systolic blood pressure and diastolic blood pressure in year 1,2,3 and 4 in turn were 0.1724, 0.5173, 0.2024, 0.5779 and 0.4347, 0.3327, 0.1669, 0.1481, respectively. There was a stronger correlation if the time between measurements was shorter. There was significant difference in the blood pressure level between obese and non-obese children. CONCLUSIONS: Obesity is associated with higher blood pressure. High blood pressure and/or obesity in childhood may be risk factors in the development of essential hypertension in adults.