PURPOSE: To evaluate the clinical and radiological results after cementless total hip arthroplasty in dysplastic hips. MATERIALS AND METHODS: This study included 36 cases that underwent total hip arthroplasty using a cementless prosthesis in our hospital from July 1990 to May 2008. The average time of of follow-up was 103.7 months. In total, 27 cases about 24 patients were women, and 8 cases about 7 patients were men. The average age at the time of operation was 55.7 years(29-80 years). In total, 26 cases were Crowe type I and 8 cases were Crowe type II. One case was Crowe type IV. Acetabular cup angles and the contact ratio between the acetabular cup and the host bone were measured, and the grafting bone was observed for absorption in the follow-up radiographs. Revision of components was defined as a failure. RESULTS: Harris hip score was improved from 55.1 points pre-operatively to 86.1 points in the last follow-up. Revision was done in 12 cases(33.3%). Altogether, 10 cases revised the acetabular cup for osteolysis and polyethylene wear and 2 cases exchanged a polyethylene liner for only liner wear. CONCLUSION: Total hip arthroplasty in the dysplastic hip using a cementless acetabular cup, not a hydroxyapatite-coated acetabular cup, showed good clinical and radiological results when the contact ratio between acetabular cup and bone was above 70%.