Controversy exists regarding the role of pelvic obliquity in hip dysplasia and cerebral palsy. Earlier authors noted such a relationship but did not confirm its existence by scientific study. The current study confirms the association of pelvic obliquity to hip dysplasia in spastic cerebral palsy. At presentation of subluxation or dislocation before surgery, 80 patients were indexed into 5 body alignment types. Reclassifications were performed with passage of time to study the natural history and effects of surgery. Hip dysplasia was found in all cases to be consistent with the forces related to pelvic obliquity.