Background： Recently, adolescent obesity was increased and tended to become obese adults, facing increased risk for diabetes, cardiovascular disease. Even before reaching adulthood, adolescent obesity already was experiencing hypertension, dyslipidemia, and diabetes mellitus. The purpose of this study was to find prevalence of obesity of high school students in Jeju island and association between obesity and cardiovascular risk factors and association between childhood obesity and adolescent obesity. Method： The study subjects were 6,064 students of twenty-two high school in Jeju island and health survey data was gathered from high school health examination data and hospital health examination data from Aug. 1999 to Dec. 1999. Adolescent obesity was evaluated by ideal body weight method in 1998 and body mass index. Cardiovascular risk factors were checked total cholesterol, systolic and diastolic blood pressure, fasting blood sugar. In 1,534 students, obesity at primary school is checked by primary and middle school health record. Results： Prevalence of obesity in Jeju island high school students is 12.6% in male students, 13.3% in female students by ideal body weight method and 8.7% in male students, 8.5% in female students by body mass index. Prevalence of obesity of male students in city area and district area of Jeju island were each 12.9%, 10.3% and that of male students in city area was significantly higher. Prevalence of obesity of female students in city area and district area of Jeju island were each 12.9%, 14.2% and not significantly different. Prevalence of obesity of male students in general and commercial school group were each 13.9%, 10.1% and that of general school group was significantly higher. In female students, Prevalence of obesity general and commercial school group was not significantly different. Total cholesterol, systolic and diastolic blood pressure were significantly associated with degree of obesity in male and female students(p＜0.05) and fasting blood sugar was only significantly associated with degree of obesity in male students(p＜0.05). In 1,514 students checked by health record, Odds ratio of obesity at primary and middle school that at high school were 12.96∼22.77 and was significantly associated. Conclusion： Prevalence of obesity of high school students in Jeju island is very high and adolescent obesity was significantly associated with cardiovascular risk factors. Mostly childhood obesity tended to become adolescent obesity and program of control of obesity at childhood and adolescence is required.