Objective: To test the hypothesis that adolescent body mass index ( BMI) tracks into adulthood and can be used as a predictor of obesity and/or central adiposity in adulthood. Method: A prospective cohort study following up 111 female and 84 male subjects who participated in dietary and anthropometric surveys when aged 12 years ( in 1979-1981) and 33 years ( in 2000-2001). At both time-points, height and weight were measured and BMI calculated. At 33 years, waist circumference ( WC) and hip circumference were also measured and waist-to-hip ratio ( WHR) calculated. Results: In the male and female participants, BMI at 12 years was associated significantly with BMI at 33 years ( R = 0.58 and 0.53, respectively, both p = 25.58 kg/m(2)) and female subjects ( BMI >= 26.05 kg/m(2)) were 83 and 64%. The corresponding probability of becoming centrally obese ( measured by WC) increased from 17 and 16% in male and female subjects of a normal weight to 58 and 59% in those being obese. Conclusions: Adolescent BMI is a good predictor of adult BMI and WC and the likelihood of becoming obese and/or centrally obese in adulthood.