The global amplitude of the movements of the trunk is the resultant of the sum of two components: the movements of the pelvic girdle and those of the vertebral segments. In order to assess the precise position of the pelvis in kinetics, we endeavored by the use of skin markers to determine whether reliable measurement points existed. The experiment showed that a line drawn from the median sacral crest at the level of S1 to the highest point of the iliac crest appeared relevant and practical for assessment of the position of the pelvic girdle in the sagittal plane.