Reorientation of the acetabulum may be necessary in the treatment of an unstable hip in children with developmental dysplasia of the hip. In 1961, Salter described the innominate osteotomy for stabilizing the reduced hip in the position of function by redirection of the acetabulum as one piece. In the present study, we describe our long-term results with this procedure. We reviewed the cases of sixty-one patients who had seventy-three Salter innominate osteotomies. At the time of the operation, the mean age of the patients was 4.1 years (range, 1.3 to 8.8 years). Radiographs made preoperatively, postoperatively, and at the time of the most recent follow-up visit were evaluated. Clinical evaluation was performed with use of the Merle d'Aubigné and Postel system as well as the Harris hip score. The mean duration of follow-up was 30.9 years (range, 26.2 to 35.4 years). There were seven true revisions (one acetabuloplasty, one triple osteotomy, and five total hip arthroplasties). With true revision as the end point, the cumulative survival rate at 35.3 years was 0.90. Fifteen of the seventy-three hips were considered a failure, which was defined as a revision or a Harris hip score of <70 points and/or a Merle d'Aubigné and Postel score of <13 points. The long-term clinical outcome was significantly influenced by the grade of dislocation on the radiographs made at the first examination (p = 0.0388) and on those made immediately preoperatively (p < 0.0001), the postoperative summarized hip factor (the radiographic grade of dysplasia) (p = 0.0002), the preoperative (p = 0.0392) and postoperative (p = 0.0072) grades of avascular necrosis of the femoral head, and the technique of reduction (p < 0.0001). When an acetabulum can be most closely restored to a normal configuration without the development of avascular necrosis, good long-term results (lasting for more than thirty years) can be expected. When open reduction is necessary, it is preferable to perform it separately prior to the Salter innominate osteotomy. The grade of dislocation at the time of the first examination and immediately preoperatively, the grade of avascular necrosis of the femoral head, and the adequacy of surgical correction are important prognostic factors for the long-term clinical result.