Clustering and tracking of serum total cholesterol, high-density lipoprotein cholesterol (HDL-C) and diastolic blood pressure were studied in children and young adults. "High-risk" individuals were defined as those having these risk factors at the age and sex specific upper tertile (lowest tertile for HDL-C). Among older boys risk factors occurred at adverse levels more often than expected by chance. Cluster-tracking was assessed as the probability of remaining in the extreme tertiles during follow-up. Approximately 25% of subjects initially at "risk" remained there for 6 years. Subjects who became high-risk individuals during the follow-up expressed greater increase in obesity indices, started to consume more saturated fat and cholesterol and became physically active less often compared to those subjects who were initially at risk, but no longer at the follow-up.