The aims of our study were to compare metal-on-metal (Metasul) and ceramic-on-ceramic (Cerasul) bearings and to evaluate the clinical and radiographic results of these 2 different hard-on-hard bearings. We conducted a prospective, randomized study on a series of 250 cementless primary total hip arthroplasties. The prostheses were similar in all aspects except for the bearing surfaces: 50% of Metasul bearing and 50% of Cerasul bearing. All the patients were evaluated both clinically and radiographically. No patient was lost to follow-up. Clinical outcomes in both groups were similar. Considering aseptic loosening as the end point for failure, the 9-year survival rate was 100% for Cerasul and 98.4% for Metasul. Neither bearing outperformed the other both radiographically and clinically. The overall 9-year survival rate was 99.2% and 97.6% in the Cerasul and Metasul groups, respectively.