In this multicenter study, submerged implants were prospectively followed to evaluate their long-term prognosis in irradiated patients. In a total of 77 patients treated for oral or neck cancer, 188 implants were consecutively placed. After a healing period, the successfully integrated implants were restored with 69 removable and 38 fixed restorations. The implants cumulative survival and success rates were evaluated over a period of at least 36 months. In addition, cumulative success rates were calculated for implant subgroups divided per implant site (mandible or maxilla), radiation dosage, and the time interval between the last irradiation and implant placement. During the healing period, 20 implants did not successfully integrate, whereas 168 implants were classified as success (including both survival and success rates). The analysis of implant subgroups showed slightly more favorable cumulative success rate for mandibular implants (98.4%) compared with maxillary implants (57.1%) and clearly better success rate for a radiation dosage minor of 50-Gy doses. A time greater than 12 months as interval between last irradiation and implant placement seems not to promote better clinical results.