Introduction: Running is a common fitness activity that is enjoyed by many older adults. Little research has been done concerning the older adult runner and research into factors that contribute to injury including impact attenuation is important. The purpose of this research was to determine if differences in impact attenuation exist between young and older adult runners. Methods: Young adult (n=8; age: 24.5±3.6 yrs.) and older adult (n=8; age: 68.9±6.3 yrs) runners ran at both a self-selected and a controlled speed of 3.3m/s. An electrogoniometer was used to measure knee angle and accelerometers attached to the head and leg measured accelerations and impact attenuation at a frequency of 1000Hz. Results: Spectral analysis revealed increased leg power and increased head power in the young adult runners. Transfer functions were similar between groups. Impact attenuation was higher for the older adult group in both the preferred and controlled running speed conditions. In the preferred running speed condition young adults ran at a faster speed, exhibited higher peak leg and peak head accelerations, more excursion flexion and contact angle flexion when compared with the older adult group. Peak head and leg acceleration and excursion flexion were also larger in the controlled running speed condition for the young adult group. Discussion: Preferred running speed appears to contribute to altered power spectra and segment acceleration in the older adults. However, other factors requiring further inquiry, contribute even in controlled speed conditions. Leg and head power spectra are altered in older runners with resulting attenuation similar between the two age groups. It appears that maintaining a stable visual field may be a larger priority in the older adult runner.