Various studies report a 0-22% per decade decline in circulatory function (VO2max) with advancing age. Twelve exercising men (E) were followed for 28 years, mean age 43 and 71 years, initial to final measurement, while 12 dropouts (C) detrained for 21 years, with a mean age from first to last measurement of 48 and 69 years, respectively. VO2 max in E changed from 45.9 to 39.4 ml.min-1.kg-1, 5% per decade, whereas C declined from 36.0 to 21.4 ml.min-1.kg-1, 19% per decade. Resting blood pressure was unchanged in E, 119/75 mmHg, whereas C rose from 128/85 to 149/90 mmHg. The data suggest that regular aerobic exercise forestalls the usual loss of circulatory function with increasing age.