Navigation procedures based on CT data were introduced into spinal surgery in 1994. Since then, the method has been used in other areas such as joint replacement, reconstructive surgery, and tumor surgery because of its high precision and reduced radiation exposure. The original CT-based spine module can be adjusted for pelvic surgery with the prerequisite that the positioning of the fragments is identical in CT and in the OR; otherwise a new dataset has to be acquired. Our experiences with CT-based navigation in pelvic surgery are explained on five percutaneous screw fixations and three tumor resections, including description of the technique. For modality-based navigation, the navigated procedure is performed in the CT suite with the advantage of immediate CT control of reduction quality and screw positioning. The technique is explained and illustrated on two cases. Fluoroscopy-based navigation has been used in trauma surgery since the late nineties. Since then, the method has been wide spread in the field of joint replacement and reconstructive surgery. Between June 2000 and December 2002, we performed 36 percutaneous screw fixations in the pelvis with postoperative x-ray and CT control. 35 of the 36 screws were placed correctly. In one screw, an anterior cortex perforation of the sacrum was seen in the CT without any neurological consequences. The Iso C 3-D fluoroscope has recently been approved for pelvic surgery. With the ability to reconstruct images, visualization of the acetabulum and the posterior pelvic ring, there is marked an improvement compare to conventional 2-D fluoroscopy. Thus, the field for navigation is also enhanced. Based on our clinical experiences, the indications for navigated techniques in pelvic and acetabular surgery are defined and illustrated.