Objective To investigate the medium-term effectiveness of straight tapered rectangular femoral prosthesis in total hip arthroplasty (THA). Methods Between May 2004 and June 2006, 58 cases (61 hips) of hip joint disease underwent THA with straight tapered rectangular femoral prosthesis and the clinical data of 43 cases (45 hips) followed up more than 6 years were retrospectively analyzed. There were 21 males (23 hips) and 22 females (22 hips) with an average age of 51.6 years (range, 25-75 years), including 12 cases (12 hips) of congenital developmental dysplasia of the hip, 1 case (1 hip) of osteoarthritis secondary to acetabular dysplasia, 1 case (1 hip) of hip deformity after poliomyelitis, 9 cases (9 hips) of femoral neck fractures, 8 cases (8 hips) of avascular necrosis of the femoral head, 8 cases (8 hips) of osteoarthritis of the hip joint, 2 cases (3 hips) of rheumatoid arthritis, and 2 cases (3 hips) of ankylosing spondylitis. Unilateral replacement was performed in 41 cases and bilateral replacement in 2 cases. The Harris score was 41.7 ± 10.4 before operation. X-ray examination was performed to analyze the location of femoral prostheses and evaluate the stability of the prosthesis-bone interface, and Harris score was used to evaluate the hip function. Results Periprosthetic fracture occurred in 3 hips, and thigh pain in 4 hips after operation. Forty-three cases (45 hips) were followed up 74-99 months (mean, 85 months). Harris score was 87.6 ± 8.3 at last follow-up, showing significant difference when compared with preoperative score (t=23.14, P=0.00). The X-ray examination showed that 9 hips had heterotopic ossification; bone resorption caused by stress shielding was observed at the proximal femur in 42 hips. But the stability of the prosthesis-bone interface was good; no infection or dislocation occurred; and no revision for aseptic loosening was performed in all cases. The survival rate of the femoral prosthesis was 100% during medium-term follow-up. Conclusion THA with straight tapered rectangular femoral prosthesis has good medium-term effectiveness.