Kinematic studies of horse and rider often suffer from their limitation to laboratory conditions because of video-based measurement techniques. To date, there are no suitable sensor-based methods published for the assessment of the rider's pelvis. The aim of this study was to reveal the possibilities and limitations of inertial sensors to assess the motion of the rider's pelvis in walk, trot, and canter, with particular attention to repeatability. Two female riders rode the same horse in repeated trials wearing an inertial sensor attached to their pelvis. Both riders were tested in walk, sitting trot, rising trot, and canter. Gait-dependent and interindividual characteristics of pelvis rotation in dressage riding under field conditions could be demonstrated. The possibility of obtaining kinematic data of horse and rider under field conditions using inertial sensors seems to be promising not only for researchers and horsemen but also for objectifying progress in therapeutic riding. (C) 2013 Elsevier Inc. All rights reserved.