To examine the long-term effects of aerobic exercise on the occurrence and time to onset of cardiovascular diagnoses, 184 initially healthy older subjects were randomized into either a long-term exercise group (Group A, n = 80), a short-term exercise group (Group B, n = 42), or a contract control group (Group C, n = 62). After completion of two years in the study, data on new cardiovascular diagnoses and time to onset of these diagnoses in each of the three groups were compared. The occurrence rates for new onset diagnoses were as follows: Group A, 2.5%; Group B, 2%; and Group C, 13%; the average time to onset was greatest for the long-term exercisers and shortest for the contact control group (P less than or equal to .02). The results suggest that a regular program of exercise may have cardiovascular benefits for those over 60 years of age.