Standing up from and sitting down to a chair are a challenging task for many elderly persons. The purpose of this study was to analyse the effects of ageing in kinematic features of each phase of motion. The study was performed on 7 young subjects (22.8 +/- 1.5 years) and 5 healthy elderly subjects (73.2 +/- 5.5 years). The kinematics of the movement were analysed by mean of an optical automatic TV processor (Elite system). Eight reflective markers were placed on left side of body. The elderly subjects showed modifications of velocity profiles of trunk and knee during the two phases of movement, an important need for an adjustment of velocity before seat-on and an inability to increase the velocity of trunk displacement in space. We suggested that these differences between young and elderly subjects, well seen during standing to sitting down, were related to deficits in postural control ability.