BACKGROUND: Maximal aerobic capacity, e.g. maximal oxygen uptake (V̇O2max), is not constant, and it has a time-dependent variation based on the condition of individual. On the other hand, arterial properties play an important role in determining aerobic performance, and lower arterial stiffness is associated with higher cardiorespiratory fitness levels. This study examined whether individual variations in maximal aerobic performance are associated with arterial stiffness. METHODS: Twenty-four (mean age, 19.8 ± 0.2 y) and 10 (mean age, 21.2 ± 0.2 y) recreationally active young men and women participated in Experiment 1 (Ex1) and in Experiment 2 (Ex2), respectively. Aerobic performance was assessed using a graded power test (Ex1) or a 1500-m time trial (Ex2). Simultaneously, brachial-ankle pulse wave velocity (baPWV) was measured as an index of arterial stiffness in both Ex1 and Ex2 before the exercise trials. In both experiments, subjects returned for measurement of baPWV and V̇O2max or 1500-m time trial at 1 month after first measurements. RESULTS: No significant differences in mean baPWV, V̇O2max or 1500-m run time were seen between first and second visits. Mean baPWV was significantly lower on days when participants showed higher V̇O2max or better 1500-m run time (P = 0.001 each) than on days when participants showed lower V̇O2max or worse 1500-m run time. In addition, a significant relationship was seen between individual changes in baPWV from first to second visits and changes in V̇O2max (P=0.0001) or 1500-m run time (P=0.04). CONCLUSION: These findings suggest that individual day-to-day variations in maximal aerobic performance are associated with variations in arterial stiffness.