Assessments of changes in gait stability due to aging and disease are predominantly based on lower extremity kinematic and kinetic data. These gait changes are also often based on comparisons at preferred speed only. The purpose of this experiment was to: (1) examine age-related changes in range of motion and coordination of segments of the upper body during locomotion; and (2) investigate the effects of a systematic walking velocity manipulation on rotational motion and coordination. Participants (n = 30) walked on a motor driven treadmill at speeds ranging from 0.2 to 1.8 m/s and were divided into three groups with mean ages of 23.3, 49.3 and 72.6 years, respectively. Seven high-speed infrared cameras were used to record three-dimensional kinematics of the pelvis, trunk and head. Dependent variables were amplitude of segmental and joint rotations, as well as relative phase to assess coordination between segments. Although no differences in stride parameters were found between the groups, age-related changes in movement amplitude in response to speed manipulations were observed for all segments and joints. Pelvic rotations in sagittal, frontal and transverse planes of motion were systematically reduced with age. Older individuals showed reduced trunk flexion-extension in the sagittal plane and increased trunk axial rotation in the transverse plane. Coordination analysis showed reduced compensatory movement between pelvis and trunk in older individuals. These findings support the importance of systematic manipulation of walking velocity and three-dimensional upper body kinematics in assessing age-related changes in locomotor stability and adaptability.