Introduction: The placement of dental implants in irradiated bone has allowed functional rehabilitation for many oral cancer patients. Nonetheless, there is only few data about implant failure in irradiated tissues and their consequences. This retrospective study aims to highlight the rate and circumstances of implant failure. Material and method: Patients treated with external radiotherapy for oral carcinoma and who received dental implants were included. Patients reconstructed with free bone flaps were excluded. Results: Eighteen patients were included. Forty implants were placed between 2004 and 2007, 8 failed, of whom one osteoradionecrosis was observed. Time interval between radiotherapy and implantation was 44.6 (6–182) months. Mean dose was 51.8 (50–66) Gy. Discussion: In the series, the implant failure rate is 20%, which corroborates the literature's data. Failures occur more often for doses over 50 Gy. The placement of dental implant in irradiated bone leads to soft tissue complications but also increases the risk of osteoradionecrosis. The recent reimbursement of dental implants in oral cancer patients by the National Social Health system will probably increase the indications. Multidisciplinary staffs should be aware of benefit/risk ratio for each patient.