INTRODUCTION: The aim of this study was to investigate the clinical and radiological results of exposure to high level of oxygen under high level of atmospheric pressure [Hyperbaric Oxygen (HBO) Therapy] in patients with Ficat Stage 1 and 2a avascular necrosis of the femoral head (AVNFH). METHODS: A retrospective examination was performed on the patients, who were administered HBO therapy and followed up due to Ficat Stage 1 and 2a AVNFH between February 2016 and November 2019.The Harris Hip Score forms, conventional radiography of the hip, and MRI were analyzed. The Ficat classification was used for grading of the aascular necrosis. RESULTS: A total of 25 patients with a mean age of 45.4 +- 11.4 years were evaluated. It was observed that the patients were administered an average of 30.4 +- 3.55 (range: 27-47) sessions of HBO therapy within an average of 40.6 +- 5.32 (range: 36-65) days. After the HBO therapy, it was found that the Ficat stage of 11 patients progressed, while the stages of two patients regressed, and seven patients remained stable (p: 0.002). While the mean total Harris Hip Score was 43.82 +- 18.55 before the procedure, it was found to be 78.47 +- 17.05 after the procedure. After the procedure, a statistically significant difference was observed in Harris Hip Scores, VAS and the range of motion measurements compared to the values obtained before the procedure (p<0.001). DISCUSSION AND CONCLUSION: HBO can be suggested as an option to be considered by the clinicians as a supportive treatment method, especially in young patients.