Aims: Malposition of the acetabular cup after THR leads to dislocations and impingement, reduces ROM and increases pressure and wear inside the cup. The use of the OrthoPilot? kinematic computer navigation technique may reduce the rate of cup malposition. Methods: After the registration of 3 pelvic bone landmarks, stereocameras record the motion of bone and instument- þxed infrared Ç ridgid bodies È. From these data the hip center, the position and direction of reamers and cup insertion instruments are calculated. Since 2001, 155 cementless plasma coated titanium pressþt cups were implanted by using this OrthoPilot¨technique. The intraop measured data of inclination and anteversion angles were compared to the angles from postop X-rays. Results: In 147 evaluated cases no speciþc complications occurred. After the þrst 35 cases minor primary technical problems could be solved. In the following cases the operation time was prolonged by 9 minutes only compared to conventional technique. The mean intra-operative value for inclination was 41¡, (29–48¡), for anteversion 15.9¡, (3–29¡). The evaluated data from the x-rays were 42¡ (34–50¡) for inclination and 10.9¡ (3–22¡) for anteversion. No dislocation occurred due to cup mal-position. Conclusions: By using kinematic navigation technique an improvement of the cup position can be shown clearly. The intended þnal cup position within the Ç safe zone È can be reached reliable. The technique is easy, safe, quick and inexpensive. The rate of postop dislocations might be reduced.