Acetabular and femoral abnormalities make total hip arthroplasty in developmental hip dysplasia a challenging procedure. We present details of long-term follow-up of a series of patients affected by developmental hip dysplasia treated with total hip arthroplasty using a cementless tapered stem. Thirty-five hips in 20 patients (18 women and 2 men) aged between 44 and 60 years (mean 51 years) were observed. Clinical evaluation was conducted using the Harris Hip Score (HHS). Radiographic evaluation consisted in standard anteroposterior and axial view radiographs of the hip. According to Crowe's classification, 25 hips had grade 2 and 10 hips grade 3 dysplasia. All patients were treated with total hip arthroplasty using a cementless tapered stem (Wagner Cone Prosthesis™). After surgery the patients were clinically and radiographically evaluated at 1, 2, 3, 6 and 12 months and annually thereafter. The average follow-up was 12 years (range 10-14 years). The average HHS was 57±7 (range 45-66) preoperatively, 90±7 (range 81-100) 12 months after surgery and 90±6 (range 83-100) at last follow-up. Radiographic evaluation demonstrated excellent osseointegration of the implants in most cases. Signs of bone resorption were present in 5 hips, but no evidence of loosening was observed and none of the implants have been revised. The tapered stem achieved adequate stability and orientation, and may be a suitable option for total hip arthroplasty for arthritis following developmental hip dysplasia.