【Abstract】 Objective To evaluate the flexibil ity of the treatment of osteoarthritis secondary to acetabular dysplasiaby total hip arthroplasty (THA) , in which the acetabular component is placed in the true acetabulum and femoral osteotomy is not performed. Methods From January 1999 to December 2005, 35 THA procedures were performed in 32 patients with 35 hips, including 6 males with 7 hips and 26 females with 28 hips, with the average age of 53 years (ranging from 28 years to 72 years). On the basis of Crowe classification, type I included 10 patients with 11 hips, type II included 14 patients with 15 hips, type III included 5 patients with 6 hips, and type IV included 3 patients with 3 hips. All patients experienced severe pain and dysfunction. In 19 cases, the leg length discrepancy was from 3 cm to 6 cm. The Harris score was 41.49 ± 10.13 before the operation. In all procedures, the soft tissue was released entirely and the acetabular component was placed in the true acetabulum, but femoral osteotomy was not performed. Results The average operation time of unilateral THA was 50 minutes. All patients were given transfusion from 2 U to 4 U. All incisions healed at the first stage. After the operation, the leg was lengthened 2-6 cm, and the two legs were equally long. The follow-up lasted for 12 to 60 months. The Harris score was 84.71 ± 9.34 after the operation, showing statistically significant differece (P lt; 0.05). According to cl inical outcomes and X-ray films, no dislocation, femoral fracture, femoral or sciatic nerve palsy was detected. Conclusion It is effective to use THA procedures for osteoarthritis secondary to acetabular dysplasia. If the soft tissue is released entirely, the leg will be lengthened 4-6 cm without nerve palsy.