OBJECTIVE: To investigate the relationship between body mass index(BMI) and blood pressure, blood lipid level, blood glucose, left ventricular structure and function in adolescents during transition period. METHODS: A vertical sectional survey on 193 pupils aged 7-11 years in primary school in 1996 was performed. 9 years later, the same research subjects aged 16-20 years were studied again in 2005. The subjects were divided into obesity,overweight and normal weight groups according to their BMI in 1996. Height, body weight, blood pressure, total cholesterol, triglyceride and blood glucose were collected and analyzed, and left ventricular structure and function were examined by echocardiography. RESULTS: Body mass index (24.71 kg/m(2)+/-4.57 kg/m(2), 20.54 kg/m(2)+/-2.84 kg/m(2) ), systolic blood pressure (117.22 mm Hg+/-17.44 mm Hg vs. 102.20 mm Hg+/-11.68 mm Hg), thickness of inter-ventricular septum and posterior wall (0.87 cm+/-0.12 cm vs. 0.77 cm+/-0.12 cm, and 0.91 cm+/-0.13 cm vs. 0.79 cm+/-0.31 cm), left ventricular mass and mass index (167.84 g+/-16.29 g vs. 128.95 g+/-63.00 g, and 88.12 g/m(2) +/-17.19 g/m(2) vs. 79.35 g/m(2)+/-39.01 g/m(2)) were found significantly higher in obesity group than in normal weight group 9 years later (P<0.05, P< 0.01 or P< 0.001). End diastolic volume and cardiac output were increased(P <0.05) and ejection fraction and fractional shortening decreased( P< 0.05). There were no differences found in cardiac diastolic function between the studied groups. CONCLUSION: The results suggested that simple obesity in childhood was an important cardiovascular risk factor when they grew into adolescents and adults. ;