To determine the prognosis and best treatment for patients who have a posterior dislocation of the hip associated with a fracture of the femoral head or neck (Grade IV, according to the classification of Stewart and Milford), we surveyed the records of 201 patients who had been treated for 203 posterior dislocations from 1958 to 1985 and selected the cases of 19 patients (19 posterior fracture-dislocations of the hip) for further review. Each of the injuries had resulted from a motor-vehicle accident. Thirteen patients had had a posterior dislocation with an associated fracture of the femoral head located either caudad or cephalad to the fovea centralis (Pipkin Type-I or Type-II injury), one had had a posterior dislocation with associated fractures of the femoral head and neck (Pipkin Type III), two had had a posterior dislocation with associated fractures of the femoral head and the acetabular rim (Pipkin Type IV), and three had had a fracture-dislocation that we could not categorize according to the Pipkin classification. Twelve patients had been treated by closed reduction for a Type-I or Type-II injury; one, by open reduction after an unsuccessful closed reduction for a Type-I injury; one, by primary total hip replacement for a Type-III injury; and three, by open reduction with screw fixation of the acetabular fracture and removal of the fragment of the head for two Type-IV injuries and one unclassified injury. An additional two patients had had both a fracture of the femoral neck and a dislocation; one hip was treated primarily with a Moore prosthesis and the other was left unreduced.(ABSTRACT TRUNCATED AT 250 WORDS)