Purpose: The purpose of this study was to evaluate the clinical and radiological results of total hip arthroplasty using a proximal modular femoral stem in patients who had secondary coxarthrosis associated with a deformed femur. Materials and Methods: Forty-two patients (45 hips) with secondary coxarthrosis were evaluated after primary total hip arthroplasty using an S-ROM proximal modular femoral stem, between January 2001 and March 2004. The average follow-up was 44 months (range, 24 to 60 months). The mean age of the patients was 48.5 years old and there was a predominance of female patients (65.5%). The preoperative diagnoses included 26 cases of developmental dysplasia of the hip, 13 cases of sequalae of LCP, 2 cases of epiphyseal dysplasia, 3 cases of sequalae of pyogenic arthritis, and 1 case of congenital coxa vara. Results: The average Harris hip score improved from 52.2 points to 85.5 points. All the femoral stems demosntrated stable fixation, which included 37 cases by bony ingrowth and 8 cases by stable fibrous ingrowth. Neither osteolysis nor progressive radiolucent lines around the femoral stems were found at the latest follow-up. Postoperative complications included: 2 cases of hip dislocations, 1 case of periprosthetic fracture, 1 case of infected cup loosening, and 1 case of sciatic nerve palsy. Overall, forty-one hips (91.9%) exhibited excellent or good clinical results at the most recent follow-up. Conclusion: For advanced secondary coxarthrosis, total hip arthroplasty with use of a proximal modular femoral stem yielded good mid-term results based on clinical and radiological criteria.