Being obese in childhood may be associated with increased cardiovascular morbidity and mortality in adulthood. We examined the relationship between obesity and overweight identified in youth and carotid artery intima-media thickness assessed in adulthood. As part of the longitudinal Cardiovascular Risk in Young Finns Study, we assessed tracking of body mass index (BMI) from youth (ages 3-18 years) to young adulthood (ages 24-39 years) in a cohort of 2,260 subjects. BMI measured in youth was significantly associated with BMI measured in adulthood. The risk of being obese in adulthood (BMI > 30 kg/m(2)) was increased by three-fold in subjects who had been overweight or obese (BMI > 80th percentile) in childhood (ages 3-9 years) and by four-fold in subjects who had been overweight or obese in adolescence (ages 12-18 years). Age and sex adjusted adult IMT values were comparable in subjects who had been consistently overweight/obese in youth and adulthood and in subjects who became obese in adulthood, 0.642 mm versus 0.634 mm, respectively. IMT values were lower (overall P