The relationship between body fat indexes, lipid and lipoprotein levels, and blood pressure was studied in 2230 children, each examined during 1973, 1976, and 1978. The children were grouped with the use of seven percentile (P) intervals of triceps skinfold thickness that were specific for race, sex, and age; cardiovascular risk factor variables were assessed over time. Of the 238 children initially in the lowest P group (less than 15P), 44% remained there, and 65% had skinfold thicknesses below 30P on the three occasions. Of the 352 children in the highest P group (greater than or equal to 85P), who were considered to be very obese, 39% remained at this level while 69% remained at 70P or greater. Of the 366 considered to be obese (greater than or equal to 70, less than 85%P), 38% remained at or above 70P. At baseline, children in the seven groups differed in weight, ponderosity (wt/ht3), systolic and diastolic blood pressures, serum triglyceride levels, and pre-beta- and beta-lipoprotein cholesterol levels. Pairwise comparison of data from children in each of the six other groups with those from children in the middle range (greater than or equal to 40, less than 60P) showed that the obese and very obese children had significantly higher systolic blood pressures (p less than .05), while only those in the highest P group had significantly greater diastolic blood pressures (p less than .05). These differences increased and diverged over time. Those in the obese and very obese groups showed a striking drop over time in alpha-lipoprotein cholesterol levels and increases in pre-beta-lipoprotein cholesterol levels and systolic blood pressure. Triglyceride levels decreased over time for the lowest and middle range groups but remained at higher levels in obese and very obese children. There was a strong tendency for tracking (remaining in the same P group over time) in lean, obese, and very obese children. Those who tracked showed definite differences in risk factor variables at the baseline level and over time when compared with the middle range group. Since consistent obesity in early life enhances cardiovascular risk, the measurement over time of skinfold thickness in children is a useful method to detect the potential for adult cardiovascular disease.