Of 54 patients with posterior dislocations of the hip of type I and type II (Stewart and Milford 1954), 47 were followed for a mean period of 6.7 years (2 to 11). Of these, 23 had dislocation with minimal lesions of the acetabulum (type I) and 24 had an avulsed dorsocranial fragment (type II). All were reduced by closed methods within six hours. The subsequent treatment of type I dislocations was conservative. At the beginning of the period type II injuries were treated conservatively, but surgery was increasingly chosen for later cases. Type I dislocations had significantly better results (p < 0.05) than type II fracture-dislocations, regardless of the method of treatment. There were no essential differences between the results of surgical and conservative treatment in type II dislocations.