OBJECTIVES: The aim of this study was to investigate the effect of age and sex on nPWV and ndI in the ascending aorta of healthy humans. BACKGROUND: Local pulse wave velocity (nPWV) and wave intensity (ndI) in the human ascending aorta have not been studied adequately, because of the need for invasive pressure measurements. However, a recently developed technique made the noninvasive determination of nPWV and ndI possible using measurements of flow velocity and arterial diameter. METHODS: Diameter and flow velocity were measured at the level of the ascending aorta in 144 healthy participants (aged 20-77 years, 66 men), using MRI. nPWV, ndI parameters; forward (FCW); backward (BCW) compression waves, forward decompression wave (FDW), local aortic distensibility (nDs) and reflection index (nRI) were calculated. RESULTS: nPWV increased significantly with age from 4.7 ± 0.3 m/s for those 20-30 years to 6.4 ± 0.2 m/s for those 70-80 years (P < 0.001) and did not differ between sexes. nDs decreased with age (5.3 ± 0.5 vs. 2.6 ± 0.2 10 1/Pa, P < 0.001) and nRI increased with age (0.17 ± 0.03 vs. 0.39 ± 0.06, P < 0.01) for those 20-30 and 70-80 years, respectively. FCW, BCW and FDW decreased significantly with age by 86.3, 71.3 and 74.2%, respectively (P < 0.001), all compared to the lowest age-band. CONCLUSION: In healthy humans, ageing results in stiffer ascending aorta, with increase in nPWV and decrease in nDs. A decrease in FCW and FDW indicates decline in left ventricular early and late systolic functions with age in healthy humans with no differences between sexes. nRI is more sensitive than BCW in establishing the effects of ageing on reflected waves measured in the ascending aorta.