Fixation of the pelvis in an oblique position constitutes a major postparalytic deformity. There are two main etiological types of pelvic obliquity: first, that due to imbalance of the abductors and adductors of the hips: second, that due to imbalance of the trunk muscles. Both types may be recognized by muscle tests at an early stage, and frequently appropriate postural treatment will cure the condition. However, if muscle imbalance persists, operation is indicated. This is best done at an early stage before the deformity has become marked. Of the late cases of deformity, those of the first type may be completely and easily cured by the division of the contracted abductor and adductor muscles, as a rule combined with the use of a fascial transplant. The second type, however, demands a complex series of corrective procedures consisting of: (1) preoperative traction by the direct skeletal method or Roger Anderson splint; (2) operative release of the contracted spinal ligaments and muscles; and (3) maintenance of the correction by fascial transplant to replace the paralyzed obliqui abdominis and quadratus lumborum, supplemented by a suitable back brace or spinal fusion. The rules for determining accurately the extent of the area to be fused have not yet been formulated.