Displaced acetabular fractures may lead to posttraumatic arthritis. Consequently, joint congruency must be restored by either conservative or operative measures. Standardized radiographs of the pelvis are prerequisites for the correct evaluation of the hip-joint. The a. p.-pelvis projection and the Judet views (obturator and iliac oblique) showing the whole pelvis are indispensable and demonstrate radiological landmarks typical of anatomical relationships and fracture characteristics. The two dimensional computertomogram is an adjunctive diagnostic measure and facilitates the evaluation of the hip joint itself. The 3DCT allows the imaging of old acetabular fractures and aids in the planning of reconstructive surgery. With the basic three projections of the hemipelvis, Letournel and Judet developed the acetabular fracture classification now accepted world-wide. Assuming the notion that the acetabulum is supported by two columns, five fracture types and five fracture type combinations are described according to involvement of the anterior or posterior columns respectively. The correct classification precedes the choice of surgical approach and is the basis for preoperative planning. The indications for surgery adhere to the principles of joint surgery. Conservative treatment may be considered only if the weight bearing joint surface of the acetabulum is congruent. Otherwise open reduction and internal fixation are indicated.