In 1949, 27 female and 26 male physical education students were studied at a mean age of 22 and 25 yr, respectively. They were restudied in 1970 and 1982. Measurements included oxygen uptake, heart rate, and pulmonary ventilation during submaximal and maximal exercise on a cycle ergometer and treadmill. After 21 yr, peak aerobic power was significantly reduced, from 2.90 to 2.18 l/min and from 4.09 to 3.28 l/min for women and men, respectively. After another 12 yr, the 1970 maxima were not reduced further. From 1949 to 1982 there was a decrease in peak heart rate from 196 to 177 beats/min in women and from 190 to 175 beats/min in men (P < 0.05). Highest pulmonary ventilation did not change significantly. At an oxygen uptake of 1.5 l/min, the heart rate was the same in 1949 as in 1982. In conclusion, the physical fitness level of the subjects was well above average for these ages. From 1970 to 1982 there was no decline in the average peak aerobic power, a finding possibly related to increased habitual physical activity.