On the basis of measurement of maximal aerobic power (VO2max) over a period of four years in a teenage population of boys (N = 102) and girls (N = 133), we studied the growth of VO2max in absolute values and in relative values: relative to whole body mass (VO2max/BM), to fat-free mass (VO2max/LBM) and to height squared (VO2max/H2). The changes in VO2max were studied in relation to chronological age (CA), skeletal age (SA), and age relative to peak height velocity (PA). Since no significant testing or measuring effects could be demonstrated and the reproducibility was high, the longitudinal design seems adequate to trace individual growth curves of VO2max. With CA VO2max increases in boys from 2.41/min at age 12+ to 3.81/min at age 17+. The increase in girls is less, from 2.31/min to 2.71/min over the same age range. VO2max/BM remained constant in boys (591/min.kg) and in girls it gradually decreased from 50 at age 12+ to 45 ml/min.kg at age 17+. The decrease in girls has been caused partly by an increase in body fat. When VO2max is aligned on PA, the results show that the peak increase coincides roughly with the age at peak height velocity. It demonstrates that in general in boys and girls during their teens no discrepancy between structural and functional growth occurs as far as VO2max is concerned.