For normal development of the hip joint to occur, there must be a delicate, genetically determined balance between growth of the acetabular and triradiate cartilages and a well-centered femoral head. This balance may be profoundly affected by the intrauterine environment. Without treatment, it is uncertain how many dysplastic, unstable hips will retain their dysplastic features throughout life. The natural history of untreated complete dislocation varies considerably and is affected by societal considerations. There may be little, if any, functional disability in many cases. Significant roentgenographic degenerative disease and poor clinical results, however, may develop in completely dislocated hips with well developed false acetabulae. In unilateral cases, ipsilateral knee deformity and pain may develop. Congenital subluxations have a particularly poor long-term outcome. A significant percentage of these patients have roentgenographic degenerative joint disease and clinical disability. The age of symptom onset and roentgenographic degenerative joint disease is related to the amount of subluxation and dysplasia. The natural history of acetabular dysplasia in the absence of subluxation is difficult to predict. Physical signs may be absent, and the diagnosis only established with symptom onset or as an incidental roentgenographic finding. While degenerative joint disease may ensue, current roentgenographic parameters are not predictive.