Between 1979 and 1993, we treated 67 hips in 58 patients with severe osteoarthritis caused by congenital dislocation of the hip, employing Bombelli's valgus-extension osteotomy. The mean age of the patients was 43.6 years (range, 23-59 years). The mean follow-up period was 9.7 years (range, 5-16 years). Thirty-three of the 67 joints were followed-up for more than 10 years after the operation. Of the 67 joints, 31 were operated on by Bombelli's valgus-extension osteotomy combined with a shelf operation (combined group), and 36 by Bombelli's valgus-extension osteotomy alone (single group). Clinical evaluation was made according to the Japanese Orthopaedic Association (JOA) hip score system (JOA hip score). In order to assess the effectiveness of this operation in regard to sustained relief from pain after the operation, Kaplan-Meier survivor analysis was performed on the basis of pain score on the JOA hip score. The end-point of the Kaplan-Meier analysis was defined as a score of less than 20 points on the pain score at the time of follow-up or conversion to total hip arthroplasty. In order to analyze the factors that exacerbated pain and to assess the effectiveness of the combined shelf operation, the degree of superior displacement of the femoral head (measured from roentgenograms) after the operation was examined in relation to the pain score. The mean JOA hip score improved, from 56.1+/-11.0 before the operation to 77.0+/-16.1 at the latest follow-up. Kaplan-Meier analysis showed a survival rate of 79.4% 10 years after the operation. Superior displacement of the femoral head had gradually progressed with time after the operation in patients with and without the combined shelf operation. Displacement of the femoral head was positively correlated with the acetabular angle of the weight-bearing surface (WBS angle) (sourcil) preoperation. The mean pain score in the combined group was significantly higher than that in the single group 6 to 9 years after the operation. The results of our assessments led us to conclude that Bombelli's valgus-extention osteotomy is satisfactory as far as clinical and radiological evaluations are concerned, as relief from the pain has continued for more than 10 years after the operation. The combined shelf operation is effective for relieving pain in severe osteoarthritis caused by congenital dislocation of the hip.