Arterial stiffness is an important factor for cardiovascular performance and a predictor of cardiovascular risk. We evaluated the effects of both acute and long-term aerobic exercise on arterial stiffness in community-dwelling healthy elderly subjects. In addition, we evaluated the relationship between the effects of long-term exercise and those of acute exercise. The study subjects were participants in the Shimanami Health Promoting Program study (J-SHIPP), which was designed to investigate factors relating to cardiovascular disease, dementia, and death (67+/-6 years). They performed mild-to-moderate aerobic exercise lasting for 30 min twice a week for 6 months. Arterial stiffness was assessed before and after the first 30-min acute exercise (n=99) and long-term 6-month aerobic training (n=40). The radial arterial augmentation index (AI) obtained from the radial pulse waveform by the tonometry method was used as a parameter of arterial stiffness. Both systolic blood pressure (SBP) and diastolic blood pressure (DBP) were significantly decreased after 30-min of aerobic exercise, however no significant change in AI was observed. On the other hand, there were significant decreases in AI (from 87 to 84%, p<0.01), SBP (from 136 to 129 mmHg, p<0.01), and DBP (from 75 to 70 mmHg, p<0.01) after the 6-month exercise period. Long-term exercise-induced changes in AI were significantly and inversely correlated with the pre-exercise AI (r=-0.40, p<0.01). In addition, AI changes after the 6-month exercise period were significantly related to those observed after first 30-min exercise (r=0.48, p<0.01). These findings indicate that apparently healthy and sedentary elderly subjects with higher AI may benefit from mild-to-moderate aerobic exercise to improve arterial stiffness.