Scoliosis is a three-dimensional deformation of the spine which is characterized by a lateral deviation of the spine and axial rotation of the vertebrae. It must be monitored frequently to be in time to start the treatment in case of progression. Nowadays, X-ray is used, but has a detrimental effect and provide only 2D data. Ultrasound would allow a frequent and 3D view on the spine and thus is ideal to follow scoliosis progression. A feasibility study on ultrasound is presented. A freehand 3D ultrasound system was used to scan the back of a volunteer. In the resulting ultrasound volume, the vertebral features such as transverse processes, laminae, and superior articular processes appear prominently along with the non-vertebral features like muscles, head of the ribs and parts of the pleura. The 3D orientation of the vertebrae, determined by the axial rotation and vertebral tilt was determined semiautomatically. The axial rotation and vertebral tilt measurements in the region of the thoracic vertebrae T4 - T9 delivered good accuracy, in other regions the accuracy was acceptable. In conclusion, imaging the human spine using ultrasound is feasible. The result provides a basis towards the aim to follow scoliosis progression using ultrasound.