Aim. To evaluate the value of cementless hip arthroplasty in the treatment of posttraumatic and atraumatic osteonecrosis (ON) of the femoral head. Methods. The study was conducted at the Department of Orthopedics and Traumatology, Military Medical Academy, between January 1st, 1999 and December 31st, 2003. Twenty five patients with 27 implanted endoprostheses, and the diagnosis of osteonecrosis of the femoral head, and radiographically confirmed Arlet-Ficat stage III and IV were evaluated retrospectively. The results were evaluated according to Harris Hip Score (HHS). The research included 10 patients with traumatically induced osteonecrosis and 15 patients (17 endoprothesis) with osteonecrosis of the femoral head. The mean age of the patients in the group with posttraumatic osteonecrosis of the femoral head was 41 (19-62) years, and in the group of the patients with atraumatic osteonecrosis of the femoral head it was 40.2 (21-53) years. Complications included one case with postoperative luxation, and one case with iatrogenic sciatic nerve palsy. Results. The average Harris Hip Scores in the group of posttraumatic osteonecrosis were 31 points preoperatively and 86 points postoperatively. In the group of osteonecrosis of atraumatic etiology, the average Harris Hip Score was 28 points preoperatively, and 77 points postoperatively. Postoperative Harris Hip Scores were compared with the Student's t-test and the results showed no statistically significant difference (p = 0,125). Conclusions. Our study did not find any significant difference between the results of posttraumatic and atraumatic osteonecrosis of the femoral head treated with cementless endoprosthesis.